Prepared by MERRILL CORPORATION
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As filed with the Securities and Exchange Commission on August 10, 2001.

Registration No. 333-    



SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM S-3

REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

CERUS CORPORATION
(Exact name of registrant as specified in its charter)

Delaware   68-0262011
(State or other jurisdiction of incorporation or organization)   (I.R.S. Employer Identification No.)

2525 Stanwell Drive, Suite 300
Concord, CA 94520
(925) 288-6000
(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)


Stephen T. Isaacs
President and Chief Executive Officer
Cerus Corporation
2525 Stanwell Drive, Suite 300
Concord, CA 94520
(925) 288-6000
(Name, address, including zip code, and telephone number, including area code, of agent for service)


Copies to:
Robert L. Jones, Esq.
Andrea Vachss, Esq.
Cooley Godward
LLP
Five Palo Alto Square
3000 El Camino Real
Palo Alto, CA 94306-2155
(650) 843-5000


Approximate date of commencement of proposed sale to the public:
From time to time after the effective date of this registration statement.


   If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box. / /

   If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box. /x/

   If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. / /

   If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. / /

   If delivery of the prospectus is expected to be made pursuant to Rule 434, please check the following box. / /

CALCULATION OF REGISTRATION FEE


Title of Each Class of
Securities to be Registered

  Proposed Maximum Aggregate
Offering Price (1)

  Amount of
Registration Fee(2)


Debt Securities (3)    

Common Stock, $0.001 par value (4)(5)    

Total   $300,000,000(6)   $75,000

(1)
The proposed maximum aggregate offering price per class of security will be determined from time to time by the registrant in connection with the issuance by the registrant of the securities registered hereunder and is not specified as to each class of security pursuant to General Instruction II.D. of Form S-3 under the Securities Act.
(2)
Calculated pursuant to Rule 457(o) under the Securities Act.
(3)
Subject to note 6 below, there is being registered hereunder an indeterminate principal amount of debt securities of the registrant as may be sold from time to time by the registrant. If any debt securities are issued at an original issue discount, then the offering price shall be in such greater principal amount at maturity as shall result in aggregate gross proceeds to the registrant not to exceed $300 million less the gross proceeds attributable to any securities previously issued pursuant to this registration statement.
(4)
Each share of the registrant's common stock being registered hereunder, if issued prior to the termination by the registrant of its preferred share rights agreement, includes Series C junior participating preferred stock purchase rights. Prior to the occurrence of certain events, the Series C junior participating preferred stock purchase rights will not be exercisable or evidenced separately from the registrant's common stock and have no value except as reflected in the market price of the share to which they are attached.
(5)
Subject to note 6 below, there is being registered hereunder an indeterminate number of shares of common stock of the registrant as may be sold from time to time by the registrant. Pursuant to Rule 457(i), this includes such indeterminate number of shares of common stock as are issuable upon conversion of any debt securities issued under this registration statement.
(6)
In no event will the aggregate offering price of all securities issued from time to time pursuant to this registration statement exceed $300,000,000, excluding accrued interest, if any, on any debt securities issued under this registration statement. The securities registered hereunder may be sold separately or as units with other securities registered hereunder.

   The registrant hereby amends this registration statement on the date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on a date that the Commission, acting pursuant to Section 8(a), may determine.




The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and we are not soliciting offers to buy these securities in any state where the offer or sale is not permitted.

PROSPECTUS (Subject to Completion)
Dated August 10, 2001

$300,000,000

CERUS CORPORATION

DEBT SECURITIES
COMMON STOCK


From time to time, we may offer and sell any of the following securities:

We will describe in a prospectus supplement the securities we are offering and selling, as well as the specific terms of the securities. Those terms may include:

You should read this prospectus and any prospectus supplements carefully before you invest. This prospectus may not be used to offer or sell any securities unless accompanied by a prospectus supplement.


Our common stock is quoted on the Nasdaq National Market under the symbol "CERS." On August 9, 2001, the last reported sale price for our common stock on the Nasdaq National Market was $62.80 per share.


INVESTING IN OUR DEBT SECURITIES OR COMMON STOCK INVOLVES A HIGH DEGREE OF RISK. SEE "RISK FACTORS" BEGINNING ON PAGE 2.


The securities may be sold directly by us to investors, through agents designated from time to time or to or through underwriters or dealers. For additional information on the methods of sale, you should refer to the section entitled "Plan of Distribution." If any underwriters are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable commissions or discounts will be set forth in a prospectus supplement. The net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement.


NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

        , 2001.



TABLE OF CONTENTS

 
  Page
ABOUT THIS PROSPECTUS   1
ABOUT CERUS   1
RISK FACTORS   2
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS   13
USE OF PROCEEDS   13
RATIO OF EARNINGS TO FIXED CHARGES   13
DESCRIPTION OF DEBT SECURITIES   14
DESCRIPTION OF CAPITAL STOCK   28
PLAN OF DISTRIBUTION   32
LEGAL MATTERS   34
EXPERTS   34
WHERE YOU CAN FIND MORE INFORMATION   34

    This prospectus is part of a registration statement we filed with the Securities and Exchange Commission. You should rely only on the information we have provided or incorporated by reference in this prospectus or any prospectus supplement. We have not authorized anyone to provide you with additional or different information. We are not making an offer of these securities in any jurisdiction where the offer is not permitted. You should assume that the information in this prospectus or any prospectus supplement is accurate only as of the date on the front of the document and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference.


    Helinx™ is a trademark of Cerus Corporation. INTERCEPT Blood System, INTERCEPT Platelet System, INTERCEPT Plasma System and INTERCEPT Red Blood Cell System are trademarks of Baxter International, Inc. This prospectus also includes trademarks or trade names owned by other parties.



ABOUT THIS PROSPECTUS

    This prospectus is part of a Registration Statement on Form S-3 that we filed with the Securities and Exchange Commission utilizing a "shelf" registration process. Under this shelf process, we may offer from time to time any combination of securities described in this prospectus in one or more offerings up to a total amount of $300,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we use this prospectus to offer securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplements may also add, update or change information contained in this prospectus. You should read both this prospectus and any prospectus supplement together with additional information described below under the heading "Where You Can Find More Information."


ABOUT CERUS

    Cerus Corporation is developing medical systems and therapeutics that provide safer and more effective treatment options to patients. Cerus' product candidates are based on its proprietary Helinx technology for controlling biological replication. Cerus' most advanced programs are focused on systems to enhance the safety of the world's blood supply. These INTERCEPT Blood Systems, based on the Helinx technology, are designed to inactivate viruses, bacteria, other pathogens and harmful white blood cells. Cerus is also pursuing therapeutic applications of the Helinx technology to treat and prevent serious diseases.

    Cerus was incorporated in California in 1991 and reincorporated in Delaware in 1996. Our principal executive offices are located at 2411 Stanwell Drive, Concord, California 94520, and our telephone number is (925) 288-6000. In this prospectus, "Cerus," "we," "us" and "our" refer to Cerus Corporation, unless the context otherwise requires.

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RISK FACTORS

    You should carefully consider the following risk factors, in addition to other information included or incorporated by reference in this prospectus and any prospectus supplement, before making an investment decision. Cerus' business faces significant risks. The risks described below are not the only risks we face. Additional risks that we do not yet know of or that we currently think are immaterial may also impair our business operations. If any of the events or circumstances described in the following risks actually occur, our business may suffer, the trading price of our common stock could decline and you may lose all or part of your investment.

Our products are in development, and there is a high risk of failure.

    We have no products that have received regulatory approval for commercial sale. Our product candidates are in various stages of development, and we face the risks of failure inherent in developing medical devices and biotechnology products based on new technologies. Our products must satisfy rigorous standards of safety and efficacy before the United States Food and Drug Administration and international regulatory authorities can approve them for commercial use. Our platelet, fresh frozen plasma, red blood cell and stem cell transplantation programs are undergoing clinical testing. Our other programs are still in the early stages of research and development. We will have to conduct significant additional research and pre-clinical (animal) and clinical (human) testing before we can file applications for product approval with the FDA and foreign regulatory agencies. Clinical trials in particular are expensive and have a high risk of failure. In addition, to compete effectively, our products must be easy to use, cost-effective and economical to manufacture on a commercial scale. Any of our product candidates may fail in the testing phase or may not attain market acceptance, which could prevent us from achieving profitability.

If our pre-clinical and clinical trials are not successful, we will be unable to commercialize our products and generate revenue.

    We must provide the FDA and foreign regulatory authorities with pre-clinical and clinical data that demonstrate our products are safe and effective before they can be approved for commercial sale. It may take us several years to complete our testing, and failure can occur at any stage of testing. We cannot rely on interim results of trials to necessarily predict their final results, and acceptable results in early trials might not be repeated in later trials. Any trial may fail to produce results satisfactory to the FDA or foreign regulatory authorities. Pre-clinical and clinical data can be interpreted in different ways, which could delay, limit or prevent regulatory approval. Negative or inconclusive results from a pre-clinical study or clinical trial or adverse medical events during a clinical trial could cause a pre-clinical study or clinical trial to be repeated or a program to be terminated, even if other studies or trials relating to a program are successful.

We may fail to complete our clinical trials on time or be unable to complete them at all.

    We typically rely on third-party clinical investigators to conduct our clinical trials and on other third-party organizations to perform data collection and analysis. As a result, we have less control over certain aspects that may delay:

    In addition, some of our clinical trials involve patient groups with rare medical conditions, which may make it difficult to identify and enroll a sufficient number of patients to complete the trials on time. Our product development costs will increase if we have delays in testing or approvals. Significant

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clinical trial delays could allow competitors to bring products to market before we do and impair our ability to commercialize our products.

Because our product candidates have not been manufactured on a commercial scale, we face manufacturing uncertainties that could limit their commercialization.

    Our product candidates, and many of their components, have never been manufactured on a commercial scale. We intend to use third-party manufacturers to produce commercial quantities of the inactivation compounds to be used in our products. These compounds have never been produced in commercial quantities. The manufacturers will need to develop new methods and processes to manufacture these compounds on a commercial scale and demonstrate to us, the FDA and foreign regulatory authorities that their commercial scale manufacturing processes comply with government regulations. It may be difficult or impossible to economically manufacture our products on a commercial scale.

    Baxter is responsible for manufacturing and assembling our pathogen inactivation systems. Baxter intends to rely on third parties to manufacture and assemble system components, many of which are customized and have not been manufactured on a commercial scale. Baxter has not produced the pathogen inactivation systems in commercial quantities and may not be able to manufacture and assemble them on an economical basis.

We depend on a limited number of suppliers to manufacture our product candidates and their components.

    A limited number of suppliers manufacture our inactivation compounds for our use in product development, including clinical trials. We have contracted with one manufacturer to provide enough S-59, the inactivation compound we use in our platelet and fresh frozen plasma systems, to meet our anticipated clinical trial and product development requirements. We have contracted with one manufacturer to produce an intermediate compound, S-301, which is used by another manufacturer which is producing S-303, the inactivation compound we use in our red blood cell systems. If any of these manufacturers cannot produce our compounds in the required quantities or to the required standards, we may face delays and shortfalls before we are able to identify alternate or additional manufacturers to meet these requirements. Also, any new manufacturer will have to prove both to us and to the FDA and foreign regulatory authorities that its manufacturing process complies with government regulations.

    Baxter has advised us that it intends to purchase certain key components of the pathogen inactivation systems from a limited number of suppliers. While we believe there are alternative suppliers for these components, it would be expensive and time-consuming to establish additional or replacement suppliers for these components. If Baxter were unable to find adequate suppliers for these components, we may be required to redesign the systems, which could lead to additional testing and clinical trials. If we were required to redesign the products, our development costs would increase, and our programs could be delayed significantly.

Our products may not achieve acceptance in or be rapidly adopted by the health care community.

    Even if our product candidates receive regulatory approval for commercial sale, physicians, patients and healthcare payors may not believe that the benefits of using our systems justify their additional cost, because the blood supply has become safer or for other reasons. We believe that our ability to successfully commercialize products will depend in part on the availability of adequate reimbursement for product costs and related treatment of blood components from governmental authorities and private health care insurers (including health maintenance organizations), which are increasingly attempting to contain health care costs by limiting both the extent of coverage and the reimbursement rate for new tests and treatments. In addition, our products may not inactivate all known pathogens,

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and the inability of our systems to inactivate certain pathogens may inhibit their acceptance. In addition, for logistical and financial reasons, the transfusion industry has not always integrated new technologies into their processes, even those with the potential to improve the safety of the blood supply. If our products fail to achieve market acceptance, we may never become profitable.

We will need to develop and test additional configurations of our platelet pathogen inactivation system to address the entire market.

    To date, we have focused almost entirely on developing our platelet pathogen inactivation system in the United States to treat apheresis platelets collected on Baxter's automated collection platform. Apheresis platelets are collected from a single donor using an automated collection machine. Currently, we estimate that the majority of platelets used in the United States are collected by apheresis, with the remainder prepared from pooled random donor platelets using a manual process. Blood centers in the United States preparing random donor platelets may be reluctant to switch to apheresis collection, and the FDA may require us to make our systems compatible with random donor platelets. In order to develop a platelet pathogen inactivation system compatible with random donor platelets, we will need to perform additional product development and testing, including clinical trials. These development activities would increase our costs significantly, and may not be successful. In addition, FDA regulations limit the time from pooling to transfusion to four hours to minimize the proliferation of bacterial contamination in the pooled product. As a result, most pooling occurs in hospitals. Our platelet system is designed for use in blood centers, not at hospitals, and is intended to permit storage of platelets for five days after treatment and pooling. The FDA's time limit between pooling and transfusion currently precludes the use of our system with pooled random donor platelets. Although our system is designed to reduce the risk of bacterial contamination, we cannot predict whether the FDA would remove this process time constraint to allow our system to be used with pooled random donor platelets.

    Baxter is one of three primary manufacturers of equipment for the collection of apheresis platelets. The equipment, design and materials used to collect the platelets vary from manufacturer to manufacturer. We have conducted our pre-clinical and clinical studies in the United States for apheresis platelets collected using only Baxter's equipment and materials. As a result, market acceptance of our platelet system for apheresis platelets will depend on market acceptance of Baxter's collection equipment. Blood centers using other equipment may be reluctant to replace their existing equipment, and the regulatory agencies may require us to make our systems compatible with other equipment. If we are required to develop platelet pathogen inactivation systems compatible with other manufacturers' equipment, or if we decide to address this broader market, we will need to perform additional product development and testing, including clinical trials. These development activities would increase our costs significantly, and may not be successful.

    We are conducting our pre-clinical and clinical studies for buffy coat platelets collected using only Baxter's platelet collection and pooling materials. As a result, market acceptance in Europe of our platelet system for buffy coat platelets will depend on market acceptance of Baxter's platelet collection and pooling sets or on our ability to develop products compatible with other manufacturers' platelet collection and pooling sets. We are conducting a clinical trial of our pathogen inactivation system for apheresis platelets in Europe using only Baxter's equipment and materials. As a result, market acceptance of our platelet system for apheresis platelets in Europe will depend on market acceptance of Baxter's collection equipment.

A small number of customers will determine market acceptance of our products.

    The market for our pathogen inactivation systems is dominated by a small number of blood collection centers. In the United States, the American Red Cross collects and distributes approximately 50% of the nation's supply of blood and blood components. Other major United States blood centers include the New York Blood Center and United Blood Services, each of which distributes

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approximately 6% of the nation's supply of blood and blood components. In Western Europe and Japan, various national blood transfusion services or Red Cross organizations collect, store and distribute virtually all of their respective nations' blood and blood components supply. Failure to properly market, price or sell our products to any of these large customers could significantly diminish potential product revenue.

We rely heavily on Baxter for development funding, manufacturing, marketing and sales.

    We have development and commercialization agreements with Baxter for our platelet, fresh frozen plasma and red blood cell pathogen inactivation systems, and we rely on Baxter for significant financial and technical contributions to these programs. Our ability to develop, manufacture and market these products successfully depends significantly on Baxter's performance under these agreements.

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Our products are subject to extensive regulation by domestic and foreign governments.

    Our products under development and anticipated future products are subject to extensive and rigorous regulation by United States local, state and federal regulatory authorities and by foreign regulatory bodies. These regulations are wide-ranging and govern, among other things:

    The FDA and other agencies in the United States and in foreign countries impose substantial requirements upon the manufacturing and marketing of products such as those we are developing. The process of obtaining FDA and other required regulatory approvals is long, expensive and uncertain. The time required for regulatory approvals is uncertain and the process typically takes a number of years, depending on the type, complexity and novelty of the product. We may encounter significant delays or excessive costs in our efforts to secure necessary approvals or licenses, or we may not be successful at all.

    Even if our product candidates receive approval for commercial sale, their marketing and manufacturing will be subject to continuing FDA and other regulatory requirements, such as requirements to comply with good manufacturing practices. The failure to comply with these requirements could result in enforcement action, which could harm our business. Later discovery of problems with a product, manufacturer or facility may result in additional restrictions on the product or manufacturer, including withdrawal of the product from the market. Regulatory authorities may also require post-marketing testing, which can involve significant expense. The government may impose new regulations, which could further delay or preclude regulatory approval of our potential products. We cannot predict the impact of adverse governmental regulation, which might arise from future legislative or administrative action.

    Distribution of our products outside the United States also is subject to extensive government regulation. These regulations, including the requirements for approvals or clearance to market, the time required for regulatory review and the sanctions imposed for violations, vary by country. Failure to obtain necessary regulatory approvals or any other failure to comply with regulatory requirements could result in reduced revenue and earnings.

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    To support our requests for regulatory approval to market our product candidates, we intend to conduct various types of studies including:

We have conducted many toxicology studies to demonstrate our product candidates' safety, and we plan to conduct additional toxicology studies throughout the product development process. At any time, the FDA and other regulatory authorities may require further toxicology or other studies to further demonstrate our products' safety, which could delay commercialization. We believe the FDA and other regulatory authorities are likely to weigh the potential risks of using our pathogen inactivation products against the incremental benefits, which may be less compelling in light of improved safety in the blood supply. In addition, our clinical development plan assumes that we will not be required to perform human clinical studies to demonstrate our systems' ability to inactivate pathogens. Although we have discussed this plan with the FDA and other regulatory authorities, they may find it unacceptable at any time and may require human clinical trials to demonstrate efficacy in inactivating pathogens. Trials of this type may be too large and expensive to be practical.

    Regulatory agencies may limit the uses, or indications, for which any of our products is approved. For example, we believe that we will be able to claim the inactivation of particular pathogens only to the extent we have laboratory or animal data to support such claims. After regulatory approval for the initial indications, further laboratory or clinical studies may be necessary to gain approval for the use of the product for additional indications.

    In addition to the regulatory requirements applicable to us and our products, there are regulatory requirements applicable to our prospective customers, the blood centers that process and distribute blood and blood products. Blood centers and others will likely be required to obtain approved license supplements from the FDA before using products processed with our pathogen inactivation systems. This requirement or FDA delays in approving these supplements may deter some blood centers from using our products. Blood centers that do submit supplements may face disapproval or delays in approval that could provide further delay or deter them from using our products. The regulatory impact on potential customers could slow or limit the potential sales of our products.

We are using prototype components in our clinical trials and have not completed their commercial design.

    The system disposables and ultraviolet light sources we use in our clinical trials are prototypes. As a result, we plan to perform studies, both pre-clinical and clinical, to demonstrate the equivalence of the prototype and the commercial design. However, regulatory agencies may require us to perform additional studies, both pre-clinical and clinical, using the commercial versions of the systems, which may increase our expenses and delay the commercialization of our products. If we fail to develop commercial versions of the systems on schedule, our competitors may be able to bring products to market before we do, which would delay or diminish our potential revenue.

We have only a limited operating history and we expect to continue to generate losses.

    We may never achieve a profitable level of operations. To date, we have engaged primarily in research and development. Our development and general and administrative expenses have resulted in substantial losses. As of June 30, 2001, we had an accumulated deficit of approximately $146.9 million. All of our products are in the research and development stage, and we have not received any revenue from product sales. We have received all of our revenue from our agreements with Baxter, Kirin and the Consortium for Plasma Science and from federal research grants and cooperative agreements. We

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will be required to conduct significant research, development, clinical testing and regulatory compliance activities for each of these products. We expect our losses to continue at least until our product candidates are commercialized and achieve significant market acceptance. Our ability to become profitable will depend on our, and our partners', ability to, among other things:


We will need additional funds.

    Our product development programs are capital-intensive. We expect to continue to spend substantial funds for our operations for the foreseeable future. We believe that our existing capital resources, together with anticipated payments from Baxter, the Consortium, Kirin and the United States government and projected interest income, will support our current and planned operations for at least the next 24 months. Our cash, liquidity and capital requirements will depend on many factors, including additional research and development needs, product testing results, regulatory requirements, competitive pressures and technological advances and setbacks.

    We may require substantial additional funds for our long-term product development, marketing programs and operating expenses. We do not know if we will be able to raise additional funds on acceptable terms. If we raise additional funds by issuing equity securities, our existing stockholders may experience substantial dilution.

We operate in a competitive industry with rapidly changing technology.

    We expect our products to encounter significant competition. Our products may compete with other approaches to blood safety and improving the outcome of stem cell transplantation currently in use, as well as with future products developed by biotechnology and pharmaceutical companies, hospital supply companies, national and regional blood centers and governmental organizations and agencies. Our success will depend in part on our ability to respond quickly to medical and technological changes through the development and introduction of new products. Product development is risky and uncertain, and we cannot assure you that we will develop our products successfully. Competitors' products or technologies may make our products obsolete or non-competitive before we are able to generate any significant revenue. Many of our competitors or potential competitors have substantially greater financial and other resources than we have. They may also have greater experience in pre-clinical testing, human clinical trials and other regulatory approval procedures. Our ability to compete successfully will depend, in part, on our ability to:

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    Several companies are developing technologies that are, or in the future may be, the basis for products that will directly compete with or reduce the market for our pathogen inactivation systems. A number of companies are specifically focusing on alternative strategies for pathogen inactivation in various blood components. In May 1998, the FDA approved solvent-detergent for use in treating FFP in the United States. If the treatment of FFP by solvent-detergent becomes a widespread practice, which has not happened to date, it could impair our ability to market our FFP pathogen inactivation system in the United States. At least one other company is currently marketing solvent-detergent based pathogen inactivation systems for FFP in Europe.

    Other groups are developing synthetic blood product substitutes and products to stimulate the growth of platelets. Development of any of these technologies could impair the potential market for our products.

Failure to attract and retain key employees will impair our business.

    Because of the scientific nature of our business, we depend on the principal members of our management and scientific staff. Our success will depend largely on our ability to attract and retain highly skilled scientific and managerial personnel. Competition for scientific and managerial personnel is particularly intense in the San Francisco Bay Area where we, together with numerous other life sciences companies, universities and research institutions, maintain our operations. The failure to maintain our management and scientific staff and to attract additional key personnel could significantly impede achievement of our research and development and commercialization objectives. Although we intend to provide incentive compensation to attract and retain our key personnel, we cannot guarantee these efforts will be successful.

We may not be able to protect our intellectual property or operate our business without infringing intellectual property rights of others.

    Our technology will be protected from unauthorized use by others only to the extent that it is covered by valid and enforceable patents or effectively maintained as trade secrets. As a result, our success depends in part on our ability to:

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    We cannot be certain that our patents or patents that we license from others will be enforceable and afford protection against competitors. Our patents or patent applications, if issued, may be challenged, invalidated or circumvented. Our patent rights may not provide us with proprietary protection or competitive advantages against competitors with similar technologies. Others may independently develop technologies similar to ours or independently duplicate our technologies. For example, a patent has recently issued to a third party covering methods to remove psoralen compounds from blood products. We have reviewed the patent and believe our work predates the invention disclosed in that patent. We are continuing to review that patent and will make a determination as to whether any action is necessary. Due to the extensive time required for development, testing and regulatory review of our potential products, our patents may expire or remain in existence for only a short period following commercialization. This would reduce or eliminate any advantage of the patents.

    We cannot be certain that we were the first to make the inventions covered by each of our issued patents or pending patent applications or that we were the first to file patent applications for such inventions. We may need to license the right to use third-party patents and intellectual property to continue development and commercialization of our products. We may not be able to acquire such required licenses on acceptable terms, if at all. If we do not obtain such licenses, we may need to design around other parties' patents or we may not be able to proceed with the development, manufacture or sale of our products.

    We may face litigation to defend against claims of infringement, assert claims of infringement, enforce our patents, protect our trade secrets or know-how, or determine the scope and validity of others' proprietary rights. Patent litigation is costly. In addition, we may require interference proceedings declared by the United States Patent and Trademark Office to determine the priority of inventions relating to our patent applications. Litigation or interference proceedings could be expensive and time consuming, and we could be unsuccessful in our efforts to enforce our intellectual property rights.

    We may rely, in certain circumstances, on trade secrets to protect our technology. However, trade secrets are difficult to protect. We protect our proprietary technology and processes, in part, by confidentiality agreements with employees and certain contractors. There can be no assurance that these agreements will not be breached, that we will have adequate remedies for any breach, or that our trade secrets will not otherwise become known or be independently discovered by competitors. To the extent that our employees, consultants or contractors use intellectual property owned by others, disputes may also arise as to the rights in related or resulting know-how and inventions.

We may be liable if our products harm people.

    We are exposed to potential liability risks inherent in the testing and marketing of medical devices and products. We may be liable if any of our products causes injury, illness or death. We intend to obtain product liability insurance before the commercial introduction of any product, but do not know whether we will be able to obtain and maintain such insurance on acceptable terms. Any insurance we obtain may not provide adequate coverage against potential liabilities. If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit commercialization of our products.

We use hazardous substances that are subject to environmental regulation.

    Our research and development involves the controlled use of hazardous materials, including certain hazardous chemicals, radioactive materials and pathogens. Accordingly, we are subject to federal, state and local laws governing the use, handling and disposal of these materials. We may incur significant costs to comply with additional environmental and health and safety regulations in the future. Although we believe that our safety procedures for handling and disposing of hazardous

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materials comply with regulatory requirements, we cannot eliminate the risk of accidental contamination or injury. If an accident occurs, we could be held liable for any damages that result.

The market price of our stock may be highly volatile.

    The market prices for our securities and those of other emerging medical device and biotechnology companies have been, and may continue to be, volatile. Announcements may have a significant impact on the market price of our common stock. Such announcements may include:

    The stock market has from time to time experienced extreme price and volume fluctuations, which have particularly affected the market prices for emerging biotechnology and medical device companies, and which have often been unrelated to the operating performance of such companies. These broad market fluctuations may adversely affect the market price of our common stock. In the past, following periods of volatility in the market price of a company's stock, securities class action litigation has occurred against the issuing company. Such litigation could result in substantial costs and a diversion of management's attention and resources, which could have a material adverse effect on our revenue and earnings. Any adverse determination in such litigation could also subject us to significant liabilities.

Anti-takeover provisions in our charter documents and under Delaware law may make it more difficult to acquire us, even though an acquisition may be beneficial to our stockholders.

    Provisions of our certificate of incorporation and bylaws could make it more difficult for a third party to acquire us, even if doing so would benefit our stockholders. These provisions:

    In November 1999, our board of directors adopted a stockholder rights plan, commonly known as a "poison pill." The provisions described above, our poison pill and provisions of the Delaware General Corporation Law relating to business combinations with interested stockholders may discourage, delay

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or prevent a third party from acquiring us, even if our stockholders might receive a premium for their shares in the acquisition over then current market prices.

The securities we are offering may not develop an active public market, which could depress the resale price of the securities.

    The securities we are offering, other than our common stock, will be new issues of securities for which there is currently no trading market. We cannot predict whether an active trading market for the securities will develop or be sustained. If an active trading market were to develop, the securities could trade at prices that may be lower than the initial offering price of the securities.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

    Some of the statements in this prospectus and the documents incorporated by reference are forward-looking statements. These statements are based on our current expectations, assumptions, estimates and projections about our business and our industry, and involve known and unknown risks, uncertainties and other factors that may cause our or our industry's results, levels of activity, performance or achievement to be materially different from any future results, levels of activity, performance or achievements expressed or implied in or contemplated by the forward-looking statements. Words such as "believe," "anticipate," "expect," "intend," "plan," "will," "may," "should," "estimate," "predict," "potential," "continue," or the negative of such terms or other similar expressions, identify forward-looking statements. In addition, any statements that refer to expectations, projections or other characterizations of future events or circumstances are forward-looking statements. Our actual results could differ materially from those anticipated in such forward-looking statements as a result of several factors more fully described under the caption "Risk Factors" and in the documents incorporated by reference. The forward-looking statements made in this prospectus relate only to events as of the date on which the statements are made.


USE OF PROCEEDS

    Unless otherwise indicated in the prospectus supplement, we currently intend to use the net proceeds from the sale of securities offered by this prospectus for general corporate purposes, including research and development, capital expenditures and to meet working capital needs. We expect from time to time to evaluate the acquisition of businesses, products and technologies for which a portion of the net proceeds may be used, although we currently are not planning or negotiating any such transactions. Pending such uses, we may invest the net proceeds in interest bearing securities.


RATIO OF EARNINGS TO FIXED CHARGES

    The following table sets forth our historical ratio of earnings to fixed charges. Earnings consist of income (loss) from continuing operations before income taxes, extraordinary items, cumulative effect of accounting changes, equity in net losses of affiliates and fixed charges. Fixed charges consist of interest expense and capitalized interest.

 
  Fiscal Year Ended December 31,
   
 
  Six Months Ended
June 30, 2001

 
  1996
  1997
  1998
  1999
  2000
Ratio of earnings to fixed charges (1)            

(1)
Earnings for the years ended December 31, 1996, 1997, 1998, 1999 and 2000 were insufficient to cover fixed charges by an amount equal to the loss before provision for income taxes for the periods.

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DESCRIPTION OF DEBT SECURITIES

    Our debt securities, consisting of notes, debentures or other evidences of indebtedness, may be issued from time to time in one or more series. We may issue the senior debt securities and the subordinated debt securities under separate indentures between us, as issuer, and the trustee or trustees identified in the prospectus supplement. The form for each type of indenture is filed as an exhibit to the registration statement of which this prospectus is a part.

    The prospectus supplement will describe the particular terms of any debt securities we may offer. The following summaries of the debt securities and the indentures are not complete and do not contain all information that you may find useful. For further information about the indentures and the debt securities, you should read the indentures and the description of the debt securities included in the prospectus supplement.

General

    The senior debt securities will constitute our unsecured and unsubordinated obligations and the subordinated debt securities will constitute our unsecured and subordinated obligations. A summary description of the subordination provisions is provided below under the caption "Terms of the Subordinated Debt Securities—Subordination". In general, however, if we declare bankruptcy, the senior debt securities will be paid in full before the subordinated debt securities will receive anything.

    You should look in the prospectus supplement for the following terms of the debt securities being offered:

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    You may present debt securities for exchange and you may present debt securities for transfer in the manner, at the places and subject to the restrictions set forth in the debt securities and the prospectus supplement. We will provide you those services without charge, although you may have to pay any tax or other governmental charge payable in connection with any exchange or transfer, as set forth in the indenture.

    Debt securities will bear interest at a fixed rate or a floating rate. Debt securities bearing no interest or interest at a rate that at the time of issuance is below the prevailing market rate may be sold at a discount below their stated principal amount. Special United States federal income tax considerations applicable to any such discounted debt securities or to certain debt securities issued at par which are treated as having been issued at a discount for United States federal income tax purposes will be described in the relevant prospectus supplement.

    We may issue debt securities with the principal amount payable on any principal payment date, or the amount of interest payable on any interest payment date, to be determined by reference to one or more currency exchange rates, securities or baskets of securities, commodity prices or indices. You may receive a payment of principal on any principal payment date, or a payment of interest on any interest payment date, that is greater than or less than the amount of principal or interest otherwise payable on such dates, depending upon the value on such dates of the applicable currency, security or basket of securities, commodity or index. Information as to the methods for determining the amount of principal or interest payable on any date, the currencies, securities or baskets of securities, commodities or indices to which the amount payable on such date is linked and certain additional tax considerations will be set forth in the applicable prospectus supplement.

Terms of the Senior Debt Securities

    Financial Information.  We will file with the trustee, within 15 days after we are required to file the same under the Securities Exchange Act of 1934, copies of the annual reports and the information, documents and other reports to be filed pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934. We intend to file all such reports, information and documents with the SEC, whether or not required by Section 13 or 15(d), and will send copies to the trustee within such 15 day period.

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    Consolidation, Merger and Sale of Assets.  We may not consolidate with, merge with or into, or sell, convey, transfer, lease, or otherwise dispose of all or substantially all of our property and assets as an entirety or substantially an entirety in one transaction or a series of related transactions to any person (other than a consolidation with or merger with or into or a sale, conveyance, transfer, lease or other disposition to a wholly-owned subsidiary with a positive net worth; provided that, in connection with any merger of us and a wholly-owned subsidiary, no consideration other than common stock in the surviving person or our common stock shall be issued or distributed to our stockholders) or permit any person to merge with or into us unless:

If the debt securities are convertible for our other securities or other entities, the person with whom we consolidate, merge or sell all of our property must make provisions for the conversion of the debt securities into securities which the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

    An event of default for a series of senior debt securities is defined under the senior indenture as being:

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    If an event of default, other than an event of default specified in the last two bullet points above, occurs with respect to an issue of senior debt securities and is continuing under the indenture, then, and in each and every such case, either the trustee or the holders of not less than 25% in aggregate principal amount of such senior debt securities of any affected series then outstanding under the indenture by written notice to us and to the trustee, if such notice is given by such holders, may, and the trustee at the request of such holders shall, declare the principal amount of and accrued interest, if any, on such affected series of senior debt securities to be immediately due and payable. Unless otherwise specified in the prospectus supplement relating to a series of debt securities originally issued at a discount, the amount due upon acceleration shall include only the original issue price of the debt securities, the amount of original issue discount accrued to the date of acceleration and accrued interest, if any.

    If the event of default occurs because we defaulted on some of our other indebtedness or because the indebtedness becomes accelerated, the trustee or the holders of at least 25% of the aggregate principal amount of the senior debt securities outstanding under the indenture, voting as one class, can accelerate all of the debt securities outstanding under the indenture. If an event of default specified in the last two bullet points above occurs with respect to us, the principal amount of and accrued interest, if any, on each issue of senior debt securities then outstanding shall be and become immediately due and payable without any notice or other action on the part of the trustee or any holder. Upon certain conditions such declarations may be rescinded and annulled and past defaults may be waived by the holders of a majority in aggregate principal amount of an affected series of senior debt securities that has been accelerated. Furthermore, subject to various provisions in the senior indenture, the holders of at least a majority in aggregate principal amount of all the then outstanding senior debt securities of all affected series, each such series voting as a separate class, by notice to the trustee, may waive an existing default or event of default with respect to such series of senior debt securities and its consequences, except a default in the payment of principal of or interest on such senior debt securities or in respect of a covenant or provision of the indenture which cannot be modified or amended without the consent of the holders of each such senior debt securities. Upon any such waiver, such default shall cease to exist, and any event of default with respect to such senior debt securities shall be deemed to have been cured, for every purpose of the senior indenture; but no such waiver shall extend to any subsequent or other default or event of default or impair any right consequent thereto. For information as to the waiver of defaults, see "Modification and Waiver."

    The holders of at least a majority in aggregate principal amount of an affected series of senior debt securities outstanding may direct the time, method and place of conducting any proceeding for

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any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to such affected series of senior debt securities. However, the trustee may refuse to follow any direction that conflicts with law or the senior indenture, that may involve the trustee in personal liability, or that the trustee determines in good faith may be unduly prejudicial to the rights of holders of such issue of senior debt securities not joining in the giving of such direction and may take any other action it deems proper that is not inconsistent with any such direction received from holders of such issue of senior debt securities. A holder may not pursue any remedy with respect to the indenture or any series of senior debt securities unless:

    These limitations, however, do not apply to the right of any holder of a debt security to receive payment of the principal of or interest, if any, on such senior debt security, or to bring suit for the enforcement of any such payment, on or after the due date for the senior debt securities, which right shall not be impaired or affected without the consent of the holder.

The senior indenture will require certain of our officers to certify, on or before a date not more than 120 days after the end of each fiscal year, as to their knowledge of our compliance with all conditions and covenants under the indenture, such compliance to be determined without regard to any period of grace or requirement of notice provided under the indenture.

    The senior indenture provides that, except as otherwise provided in this paragraph, we may discharge our obligations with respect to an issue of senior debt securities and the indenture with respect to such series of senior debt securities:

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    With respect to the first bullet point, only our obligations to compensate and indemnify the trustee and our right to recover excess money held by the trustee under the indenture shall survive. With respect to the second bullet point, only our obligations with respect to the issue of defeased senior debt securities to execute and deliver such senior debt securities for authentication, to set the terms of such senior debt securities, to maintain an office or agency in respect of such senior debt securities, to have moneys held for payment in trust, to register the transfer or exchange of such senior debt securities, to deliver such senior debt securities for replacement or to be canceled, to compensate and indemnify the trustee and to appoint a successor trustee, and our right to recover excess money held by the trustee shall survive until such senior debt securities are no longer outstanding. Thereafter, only our obligations to compensate and indemnify the trustee, and our right to recover excess money held by the trustee shall survive.

    The senior indenture also provides that, except as otherwise provided in this paragraph, we:

provided that the following conditions shall have been satisfied:

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    Subsequent to legal defeasance under the first bullet point above, our obligations with respect to the issue of defeased senior debt securities to execute and deliver such senior debt securities for authentication, to set the terms of such senior debt securities, to maintain an office or agency in respect of such senior debt securities, to have moneys held for payment in trust, to register the transfer or exchange of such senior debt securities, to deliver such debt securities for replacement or to be canceled, to compensate and indemnify the trustee and to appoint a successor trustee, and its right to recover excess money held by the trustee shall survive until such senior debt securities are no longer outstanding. After such senior debt securities are no longer outstanding, in the case of legal defeasance under the first bullet point above, only our obligations to compensate and indemnify the trustee and our right to recover excess money held by the trustee shall survive.

    We and the trustee may amend or supplement the senior indenture or the senior debt securities without notice to or the consent of any holder:

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    Subject to certain conditions, without prior notice to any holder of an issue of senior debt securities, modifications and amendments of the senior indenture may be made by us and the trustee with the written consent of the holders of a majority in principal amount of such series of senior debt securities, and compliance by us with any provision of the indenture with respect to such series of senior debt securities may be waived by written notice to the trustee by the holders of a majority in principal amount of such series of senior debt securities outstanding; provided, however, that each affected holder must consent to any modification, amendment or waiver that,

    It shall not be necessary for the consent of the holders under this section of the indenture to approve the particular form of any proposed amendment, supplement, or waiver, but it shall be sufficient if such consent approves the substance thereof. After an amendment, supplement, or waiver under this section of the indenture becomes effective, we must give to the holders affected thereby a notice briefly describing the amendment, supplement, or waiver. We will mail supplemental indentures to holders upon request. Any failure by us to mail such notice, or any defect therein, shall not, however, in any way impair or affect the validity of any such supplemental indenture or waiver.

    With respect to any issue of senior debt securities, neither we nor any of our subsidiaries will, directly or indirectly, pay or cause to be paid any consideration, whether by way of interest, fee, or otherwise, to any holder of any such senior debt securities for or as an inducement to any consent, waiver, or amendment of any of the terms or provisions of such series of senior debt securities or the indenture with respect to such series of senior debt securities unless such consideration is offered to be paid or agreed to be paid to all holders of such senior debt securities of such series that consent, waive, or agree to amend in the time frame set forth in the solicitation documents relating to such consent, waiver, or agreement.

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    The senior indenture provides that no recourse shall be had under or upon any of our obligations, covenants or agreements in the indenture or any supplemental indenture, or in any of the senior debt securities or because of the creation of any indebtedness represented thereby, against any of our incorporators, stockholders, officers, directors or employees or any of their successor persons under any law, statute or constitutional provision or by the enforcement of any assessment or by any legal or equitable proceeding or otherwise. Each holder, by accepting the senior debt securities, waives and releases all such liability.

    The senior indenture provides that, except during the continuance of a default, the trustee will not be liable, except for the performance of such duties as are specifically set forth in the senior indenture. If an event of default has occurred and is continuing, the trustee will exercise such rights and powers vested in it under the senior indenture and will use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person's own affairs.

    The indentures and the debt securities will be governed by, and construed in accordance with, the internal laws of the State of New York.

    We may have normal banking relationships with the trustees under the indentures in the ordinary course of business.

Terms of the Subordinated Debt Securities

    Other than the terms of the subordinated indenture and subordinated debt securities relating to subordination, or otherwise as described in the prospectus supplement relating to a particular series of subordinated debt securities, the terms of the subordinated indenture and subordinated debt securities are identical, in all material respects, to the terms of the senior indenture and senior debt securities.

    The payment of the principal of, premium, if any, interest on and all other amounts payable under the subordinated debt securities is subordinated, to the extent provided in the indenture, to the prior payment in full of all senior indebtedness (as defined in the indenture and described below). This subordination will not prevent the occurrence of any event of default. The subordinated debt securities are also structurally subordinated to all indebtedness and other liabilities, including trade payables and lease obligations, if any, of our subsidiaries.

    Upon any distribution of our assets upon any dissolution, winding up, bankruptcy, insolvency, liquidation, reorganization, receivership or similar proceeding relating to us or our property, an assignment for the benefit of creditors or any marshaling of our assets or liabilities, the holders of senior indebtedness will be entitled to receive payment in full, in cash or other payment satisfactory to the holders of senior indebtedness, of all obligations due in respect of the senior indebtedness before the holders of the subordinated debt securities will be entitled to receive any payment of the principal, premium, if any, interest on, or any other amounts payable in respect of the subordinated debt securities. Until all obligations with respect to senior indebtedness are paid in full in cash or other payment is made satisfactory to the holders of senior indebtedness, any payment on the subordinated debt securities to which the holders of subordinated debt securities would be entitled shall be made to

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the holders of senior indebtedness. By reason of the subordination, in the event of our dissolution, winding up, bankruptcy, insolvency, liquidation, reorganization, receivership or similar proceeding relating to us or our property, an assignment for the benefit of creditors or any marshaling of our assets or liabilities, holders of senior indebtedness may receive more, ratably, and the holders of subordinated debt securities may receive less, ratably, than our other creditors.

    In the event of any acceleration of the subordinated debt securities because of an event of default, the holders of any senior indebtedness then outstanding would be entitled to payment in full in cash or other payment satisfactory to the holders of senior indebtedness of all obligations in respect of the senior indebtedness before the holders of the subordinated debt securities would be entitled to receive any payment or distribution. The indenture will require that we promptly notify holders of senior indebtedness if payment of the subordinated debt securities is accelerated because of an event of default.

    We also may not make any payment upon or in respect of the subordinated debt securities, including upon redemption, if:

    Payments on the subordinated debt securities may and shall be resumed (a) in case of a payment default, upon the date on which the payment default is cured or waived or ceases to exist and (b) in case of a non-payment default, the earlier of the date on which the nonpayment default is cured, waived or ceases to exist or 179 days after the date on which the applicable payment blockage notice is received, if the majority of the designated senior indebtedness has not been accelerated, or in the case of any lease, 179 days after notice is received if we have not received notice that the lessor under such lease has exercised its rights to terminate the lease or require us to make an irrevocable offer to terminate the lease following an event of default under the lease. No new period of payment blockage may be commenced pursuant to a payment blockage notice unless and until 365 days have elapsed since the initial effectiveness of the immediately prior payment blockage notice and all scheduled payments of principal, premium, if any, and interest on the subordinated debt securities that have come due have been paid in full in cash. No non-payment default that existed or was continuing on the date of delivery of any payment blockage notice to the trustee shall be, or shall be made, the basis for a subsequent payment blockage notice.

    If, notwithstanding the foregoing, the trustee or any holder of the subordinated debt securities receives any payment or distribution of our assets of any kind in contravention of any of the subordination provisions of the indenture, whether in cash, property or securities, including, without limitation, by way of set-off or otherwise, in respect of the subordinated debt securities before all senior indebtedness is paid in full in cash or other payment satisfactory to holders of senior indebtedness, then that payment or distribution will be held by the recipient in trust for the benefit of holders of senior indebtedness of their representatives to the extent necessary to make payment in full in cash or payment satisfactory to the holders of senior indebtedness of all senior indebtedness remaining unpaid, after giving effect to any concurrent payment or distribution, or provision therefor, to or for the holders of senior indebtedness.

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    The term "designated senior indebtedness" is defined in the indenture to mean our obligations under any senior indebtedness with respect to which the instrument creating or evidencing the same or the assumption or guarantee thereof (or related agreements or documents to which we are a party) expressly provides that the senior indebtedness shall be "designated senior indebtedness" for purposes of the indenture; provided that the instrument, agreement or other document may place limitations and conditions on the right of that senior indebtedness to exercise the rights of designated senior indebtedness. If any payment made to any holder of any designated senior indebtedness or its representative with respect to such designated senior indebtedness is rescinded or must otherwise be returned by such holder or representative upon the insolvency, bankruptcy or reorganization of us or otherwise, our reinstated indebtedness arising as a result of such rescission or return shall constitute designated senior indebtedness effective as of the date of such rescission or return.

    The term "indebtedness" is defined in the indenture to mean, with respect to any person (as defined in the indenture), and without duplication:

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    The term "senior indebtedness" is defined in the indenture to mean the principal of, premium, if any, interest (including all interest accruing subsequent to the commencement of any bankruptcy or similar proceeding, whether or not a claim for post-petition interest is allowable as a claim in the proceeding) and rent payable on, or termination payment with respect to, or in connection with, and all fees, costs, expenses and other amounts accrued or due on or in connection with, our indebtedness (as defined), whether outstanding on the date of the indenture or thereafter created, incurred, assumed, guaranteed or in effect guaranteed by us (including all refinancings, replacements, deferrals, renewals, extensions or refundings of, or amendments, modifications or supplements to, the foregoing), unless in the case of any particular indebtedness the instrument creating or evidencing the same or the assumption or guarantee thereof expressly provides that the indebtedness shall not be senior in right of payment to the subordinated debt securities or expressly provides that the indebtedness is pari passu or junior to the subordinated debt securities. The term "senior indebtedness" shall include all "designated senior indebtedness." Notwithstanding the foregoing, the term senior indebtedness shall not include our indebtedness to any of our subsidiaries, a majority of the voting stock of which is owned, directly or indirectly, by us.

    As of June 30, 2001, we had approximately $96,000 of indebtedness outstanding that would have constituted senior indebtedness. The indenture will not limit the amount of additional indebtedness, including senior indebtedness, which we can create, incur, assume or guarantee, nor will the indenture limit the amount of indebtedness or other liabilities that any subsidiary can create, incur, assume or guarantee.

    We are obligated to pay reasonable compensation to the trustee and to indemnify the trustee against specified losses, liabilities or expenses incurred by it in connection with its duties relating to the notes. The trustee's claims for these payments will generally be senior to those of the holders of the subordinated debt securities in respect of all funds collected or held by the trustee.

Convertible Debt Securities

    The terms, if any, on which debt securities being offered may be exchanged for or converted into other debt securities or shares of preferred stock, common stock or our other securities or rights (including rights to receive payments in cash or securities based on the value, rate or price of one or more specified commodities, currencies or indices) or securities of other issuers or any combination of the foregoing will be set forth in the prospectus supplement for the debt securities being offered.


Global Securities

    We may issue the debt securities in the form of one or more fully registered global securities that will be deposited with a depositary or with a nominee for a depositary identified in the prospectus supplement relating to such series and registered in the name of the depositary or its nominee. In that case, one or more global securities will be issued in a denomination or aggregate denominations equal to the portion of the aggregate principal or face amount of outstanding registered securities of the series to be represented by such global securities. Unless and until the depositary exchanges a global security in whole for securities in definitive registered form, the global security may not be transferred except as a whole by the depositary to a nominee of the depositary or by a nominee of the depositary to the depositary or another nominee of the depositary or by the depositary or any of its nominees to a successor of the depositary or a nominee of such successor.

    The specific terms of the depositary arrangement with respect to any portion of a series of securities to be represented by a global security will be described in the prospectus supplement relating to such series. We anticipate that the following provisions will apply to all depositary arrangements.

    Ownership of beneficial interests in a global security will be limited to persons that have accounts with the depositary for such global security known as "participants" or persons that may hold interests

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through such participants. Upon the issuance of a global security, the depositary for such global security will credit, on its book-entry registration and transfer system, the participants' accounts with the respective principal or face amounts of the securities represented by such global security beneficially owned by such participants. The accounts to be credited shall be designated by any dealers, underwriters or agents participating in the distribution of such securities. Ownership of beneficial interests in such global security will be shown on, and the transfer of such ownership interests will be effected only through, records maintained by the depositary for such global security (with respect to interests of participants) and on the records of participants (with respect to interests of persons holding through participants). The laws of some states may require that certain purchasers of securities take physical delivery of such securities in definitive form. Such limits and such laws may impair the ability to own, transfer or pledge beneficial interests in global securities.

    So long as the depositary for a global security, or its nominee, is the registered owner of such global security, such depositary or such nominee, as the case may be, will be considered the sole owner or holder of the securities represented by such global security for all purposes under the applicable indenture, warrant agreement, purchase contract, declaration, guaranteed trust preferred securities guarantee or unit agreement. Except as set forth below, owners of beneficial interests in a global security will not be entitled to have the securities represented by such global security registered in their names, will not receive or be entitled to receive physical delivery of such securities in definitive form and will not be considered the owners or holders thereof under the applicable indenture, warrant agreement, purchase contract, declaration, guaranteed trust preferred securities guarantee or unit agreement. Accordingly, each person owning a beneficial interest in a global security must rely on the procedures of the depositary for such global security and, if such person is not a participant, on the procedures of the participant through which such person owns its interest, to exercise any rights of a holder under the applicable indenture, warrant agreement, purchase contract, declaration, guaranteed trust preferred securities guarantee or unit agreement. We understand that under existing industry practices, if we request any action of holders or if an owner of a beneficial interest in a global security desires to give or take any action which a holder is entitled to give or take under the applicable indenture, warrant agreement, purchase contract, declaration, guaranteed trust preferred securities guarantee or unit agreement, the depositary for such global security would authorize the participants holding the relevant beneficial interests to give or take such action, and such participants would authorize beneficial owners owning through such participants to give or take such action or would otherwise act upon the instructions of beneficial owners holding through them.

    Principal, premium, if any, and interest payments on debt securities, and any payments to holders with respect to warrants, purchase contracts, preferred securities, guaranteed trust preferred securities guarantee or units, represented by a global security registered in the name of a depositary or its nominee will be made to such depositary or its nominee, as the case may be, as the registered owner of such global security. None of us, the trustees, the warrant agents, the unit agents or any of our other agents, agent of the trustees or agent of the warrant agents or unit agents will have any responsibility or liability for any aspect of the records relating to or payments made on account of beneficial ownership interests in such global security or for maintaining, supervising or reviewing any records relating to such beneficial ownership interests.

    We expect that the depositary for any securities represented by a global security, upon receipt of any payment of principal, premium, interest or other distribution of underlying securities or commodities to holders in respect of such global security, will immediately credit participants' accounts in amounts proportionate to their respective beneficial interests in such global security as shown on the records of such depositary. We also expect that payments by participants to owners of beneficial interests in such global security held through such participants will be governed by standing customer instructions and customary practices, as is now the case with the securities held for the accounts of

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customers in bearer form or registered in "street name," and will be the responsibility of such participants.

    If the depositary for any securities represented by a global security is at any time unwilling or unable to continue as depositary or ceases to be a clearing agency registered under the Securities Exchange Act of 1934, and we do not appoint a successor depositary registered as a clearing agency under the Securities Exchange Act of 1934 within 90 days, we will issue such securities in definitive form in exchange for such global security. In addition, we may at any time and in our sole discretion determine not to have any of the securities of a series represented by one or more global securities and, in such event, will issue securities of such series in definitive form in exchange for all of the global security or securities representing such securities. Any securities issued in definitive form in exchange for a global security will be registered in such name or names as the depositary shall instruct the relevant trustee, warrant agent or our other relevant agent. We expect that such instructions will be based upon directions received by the depositary from participants with respect to ownership of beneficial interests in such global security.

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DESCRIPTION OF CAPITAL STOCK

    Our authorized capital stock consists of 50,000,000 shares of common stock, par value $.001 per share, and 5,000,000 shares of preferred stock, par value $.001 per share.

Common Stock

    As of July 31, 2001, there were 15,714,178 shares of common stock issued and outstanding

    The holders of common stock are entitled to one vote for each share held of record on all matters submitted to a vote of the stockholders. Subject to preferences that may be applicable to any outstanding shares of the preferred stock, the holders of common stock are entitled to receive ratably such dividends as may be declared by the board of directors out of funds legally available therefor. In the event of a liquidation, dissolution or winding up of our company, holders of the common stock are entitled to share ratably in all assets remaining after payment of liabilities and the liquidation preferences of any outstanding shares of preferred stock. Holders of common stock have no preemptive rights and no right to convert their common stock into any other securities. There are no redemption or sinking fund provisions applicable to the common stock. All outstanding shares of common stock are, and all shares of common stock to be outstanding upon the closing of this offering will be, fully paid and nonassessable.

Preferred Stock

    As of July 31, 2001, there were 5,000 shares of Series A preferred stock and 3,327 shares of Series B preferred stock issued and outstanding.

    Pursuant to our Restated Certificate of Incorporation, our board of directors has the authority, without further action by the stockholders, to issue up to 5,000,000 shares of preferred stock in one or more series and to fix the designations, powers, preferences, privileges and relative participating, optional or special rights and the qualifications, limitations or restrictions thereof, including dividend rights, conversion rights, voting rights, terms of redemption and liquidation preferences, any or all of which may be greater than the rights of the common stock. The board of directors, without stockholder approval, can issue preferred stock with voting, conversion or other rights that could adversely affect the voting power and other rights of the holders of common stock. Preferred stock could thus be issued quickly with terms calculated to delay or prevent a change in control of our company or make removal of management more difficult. Additionally, the issuance of preferred stock may have the effect of decreasing the market price of the common stock and may adversely affect the voting and other rights of the holders of common stock.

    Series A Preferred Stock.  The holders of Series A preferred stock have no voting rights, except as required under the General Corporation Law of Delaware, and as follows: Without first obtaining the affirmative vote or written consent of the holders of at least a majority of the outstanding shares of Series A preferred stock, voting as a separate class, we may not effect any merger or consolidation in which Cerus is not the surviving entity, or any merger, consolidation or other transaction in which our common stock becomes no longer publicly traded, unless the surviving entity in such a transaction has provided certain contractual rights for the benefit of the holders of Series A preferred stock. Upon any liquidation, dissolution, or winding up of our company, before any payment or distribution of assets shall be made to the holders of common stock, the holders of Series A preferred stock shall be entitled to be paid out of our assets an amount per share of Series A preferred stock equal to $1,000.00, the original issue price.

    We have the right to redeem, at the original issue price, all or a portion of the Series A preferred stock upon the approval of a NDA or PMA by the FDA or the comparable approval in Europe under the Platelet Agreement. We and the holders of Series A preferred stock may require redemption, at

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the original issue price, of all of the Series A preferred stock upon the termination for any reason of the Platelet Agreement or upon the cessation for any reason of cooperative development work, as specified in the Platelet Agreement. In addition, immediately prior to consummation of a merger or consolidation in which Cerus is not the surviving entity, or any merger, consolidation or other transaction in which our common stock becomes no longer publicly traded, we have the right to redeem all of the Series A preferred stock then outstanding at the original issue price.

    The Series A preferred stock automatically converts, at 120% of the average closing price of the common stock for the 30 trading days prior to and including the trading day immediately prior to the approval of a NDA or PMA by the FDA or the comparable approval in Europe under the Platelet Agreement. If the Platelet Agreement is terminated or cooperative development work under the Platelet Agreement ceases, and a redemption notice has not been sent by us or the holder of the Series A preferred stock, the Series A preferred stock shall automatically convert, at a price equal to the average closing price of the common stock for the 30 trading days commencing with the 15th trading day prior to the date of termination or cessation, on the 15th day following date on which such conversion shall occur shall be the 15th day following the Termination Payment Date, as such term is defined in the Platelet Agreement. However, in the event that the approval of our stockholders is required pursuant to Rule 4460(i) of the Nasdaq Stock Market prior to the issuance of any of the shares of common stock issuable upon conversion of the Series A preferred stock, we must obtain such approval by the applicable conversion date, or, if such approval is not obtained, we must redeem any shares of Series A preferred stock that would be convertible into shares of common stock in excess of the limitation specified in Rule 4460(i).

    Neither the Series A preferred stock nor any right to receive redemption payments may be assigned, transferred, hypothecated or otherwise alienated by a Series A preferred stock holder without our prior written consent, except (i) in connection with, and to the transferee of, all or substantially all of the business and assets of such holder, or (ii) to a direct or indirect wholly owned subsidiary of Baxter.

    Series B Preferred Stock.  The holders of Series B preferred stock have no voting rights, except as required under the General Corporation Law of Delaware, and as follows: Without first obtaining the affirmative vote or written consent of the holders of at least a majority of the outstanding shares of each series of preferred stock that is designated as a sub-series of Series B preferred stock, voting together as a separate class, we may not authorize or issue shares of any class or series of stock, or reclassify any class or series of stock, into shares having preference or priority over the Series B preferred stock as to voting, liquidation preference or conversion rights. Upon any liquidation, dissolution, or winding up of our company, before any payment or distribution of assets shall be made to the holders of common stock, Series A preferred stock or any other class or series of stock ranking junior to the Series B preferred stock with respect to liquidation preference, the holders of Series B preferred stock shall be entitled to be paid out of the assets of the company an amount per share of Series B preferred stock equal to the original issue price.

    We will have the right to redeem, at the original issue price, all of the Series B preferred stock at any time. At any time after the one-year anniversary of the date of issuance of the Series B preferred stock, each share of Series B preferred stock may, at the option of the holder, be converted at any time into that number of shares of common stock equal to the original issue price divided by 100. However, in the event that the approval of our stockholders is required pursuant to Rule 4460(i) prior to the issuance of any of the shares of common stock issuable upon conversion of the Series B preferred stock, we must obtain such approval by the conversion date, or, if such approval is not obtained, we must redeem any shares of Series B preferred stock that would be convertible into shares of common stock in excess of the limitation specified in Rule 4460(i).

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    Neither the Series B preferred stock nor any right to receive redemption payments may be assigned, transferred, hypothecated or otherwise alienated by a Series B preferred stock holder without our prior written consent, except (i) in connection with, and to the transferee of, all or substantially all of the business and assets of such holder, or (ii) to a direct or indirect wholly owned subsidiary of Baxter.

Antitakeover Effects of Provisions of Charter Documents and Delaware Law

    Charter Documents.  Our Restated Certificate and Bylaws include a number of provisions that may have the effect of deterring hostile takeovers or delaying or preventing changes in control or management of our company. First, our board of directors is classified into three classes of directors. Under Delaware law, directors of a corporation with a classified board may be removed only for cause unless the corporation's certificate of incorporation provides otherwise. Our Restated Certificate does not provide otherwise. In addition, the Restated Certificate provides that all stockholder action must be effected at a duly called meeting of stockholders and not by a consent in writing. Further, our Bylaws limit who may call special meetings of the stockholders. Our Restated Certificate does not include a provision for cumulative voting for directors. Under cumulative voting, a minority stockholder holding a sufficient percentage of a class of shares may be able to ensure the election of one or more directors. Finally, our Bylaws establish procedures, including advance notice procedures, with regard to the nomination of candidates for election as directors and stockholder proposals. These and other provisions of our Restated Certificate and Bylaws and Delaware law could discourage potential acquisition proposals and could delay or prevent a change in control or management of our company.

    Delaware Takeover Statute.  We are subject to the provisions of Section 203 of the Delaware General Corporation Law. In general, the statute prohibits a publicly held Delaware corporation from engaging in a business combination with an interested stockholder for a period of three years after the date of the transaction in which the person became an interested stockholder, unless the business combination is approved in a prescribed manner. For purposes of Section 203, a business combination includes a merger, asset sale or other transaction resulting in a financial benefit to the interested stockholder, and an interested stockholder is a person who, together with affiliates and associates, owns (or within three years prior, did own) 15% or more of the corporation's voting stock.

Rights Plan

    In November 1999, our board of directors adopted a Stockholder Rights Plan, pursuant to which one preferred share purchase right was issued as a dividend for each outstanding share of our common stock. Each purchase right entitles the registered holder to purchase from Cerus one one-hundredth of a share of Series C junior participating preferred stock at a price of $170 per one one-hundredth of a preferred share, subject to adjustment. The purchase rights will become exercisable when a person or group (except with respect to certain Cerus stockholders), acquires 15% or more of our outstanding common stock or ten business days after commencement or announcement of a tender or exchange offer for 15% or more of our outstanding common stock. If a person or group acquires 15% or more of our outstanding common stock, all rightsholders except such buyer will be entitled to acquire Cerus common stock at a discount.

    Preferred shares purchasable upon exercise of the purchase rights will not be redeemable. Each preferred share will be entitled to a minimum preferential quarterly dividend payment of $1.00 but will be entitled to an aggregate dividend of 100 times the dividend declared per share of common stock. In the event of liquidation, the holders of the preferred shares would be entitled to receive an aggregate payment equal to 100 times the payment made per share of common stock. Each preferred share will have 100 votes, voting together with the common stock. Finally, in the event of any merger, consolidation or other transaction in which shares of common stock are exchanged, each preferred share will be entitled to receive 100 times the amount of consideration received per share of common

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stock. These rights are protected by customary anti-dilution provisions. The preferred shares rank junior to any other series of our preferred stock. These rights will expire on November 3, 2009, unless earlier redeemed or exchanged by Cerus.

Registration Rights

    Pursuant to an agreement between us and the holders (or their permitted transferees) of approximately 4.3 million shares of common stock and common stock issuable upon conversion of Series A preferred stock, these holders are entitled to certain rights with respect to the registration of such shares under the Securities Act. If we propose to register our common stock, subject to certain exceptions, under the Securities Act, the holders are entitled to notice of the registration and are entitled to include, at our expense, such shares therein, provided that the managing underwriters have the right to limit the number of such shares included in the registration. In addition, certain of the holders may require us, on no more than two occasions and, on one of such occasions, at our expense, to file a registration statement under the Securities Act with respect to their shares of common stock. Such rights may not be exercised until six months after the closing of this offering. Further, certain holders, at their expense, may require us to register the shares on Form S-3 when such form is available to us, subject to certain conditions and limitations. Such right expires in April 2009.

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PLAN OF DISTRIBUTION

    We may sell the securities separately or together:

    We may sell the securities from time to time in one or more transactions at a fixed price or prices, which may be changed from time to time:

    We will set forth in a prospectus supplement the terms of the offering of securities, including:

    If we use underwriters for a sale of securities, the underwriters will acquire the securities for their own account. The underwriters may resell the securities in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. The underwriters will be obligated to purchase all the securities of the series offered if they purchase any of the securities of that series. We may use underwriters with whom we have a material relationship. We will describe in the prospectus supplement naming the underwriter the nature of any such relationship.

    Underwriters, dealers or agents may receive compensation in the form of discounts, concessions or commissions from us or our purchasers (as their agents in connection with the sale of securities). These underwriters, dealers or agents may be considered to be underwriters under the Securities Act. As a result, discounts, commissions or profits on resale received by the underwriters, dealers or agents may be treated as underwriting discounts and commissions. The prospectus supplement will identify any such underwriter, dealer or agent, and describe any compensation received by them from us. Any initial public offering price and any discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time.

    We may authorize agents or underwriters to solicit offers by certain types of institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe the conditions to these contracts and the commissions we must pay for solicitation of these contracts in the prospectus supplement.

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    Underwriters, dealers and agents may be entitled to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments made by the underwriters, dealers or agents, under agreements between us and the underwriters, dealers and agents.

    We may grant underwriters who participate in the distribution of securities an option to purchase additional securities to cover over-allotments, if any, in connection with the distribution.

    All debt securities will be new issues of securities with no established trading market. Underwriters involved in the public offering and sale of debt securities may make a market in the debt securities. However, they are not obligated to make a market and may discontinue market-making activity at any time. No assurance can be given as to the liquidity of the trading market for any debt securities.

    Underwriters or agents and their associates may be customers of, engage in transactions with or perform services for us in the ordinary course of business.

    Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Overallotment involves sales in excess of the offering size, which create a short position. Stabilizing transactions permit bids to purchase the underlying security so long as the stabilizing bids do not exceed a specified maximum. Short covering transactions involve purchases of the securities in the open market after the distribution is completed to cover short positions. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions. Those activities may cause the price of the securities to be higher than it would otherwise be. If commenced, the underwriters may discontinue any of the activities at any time.

    Any underwriters who are qualified market makers on the Nasdaq National Market may engage in passive market making transactions in the securities on the Nasdaq National Market in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker's bid, however, the passive market maker's bid must then be lowered when certain purchase limits are exceeded.

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LEGAL MATTERS

    The validity of the issuance of the securities offered hereby will be passed upon by Cooley Godward LLP, Palo Alto, California.


EXPERTS

    Ernst & Young LLP, independent auditors, have audited our financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2000, as set forth in their report, which is incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on Ernst & Young LLP's report, given on their authority as experts in accounting and auditing.


WHERE YOU CAN FIND MORE INFORMATION

    We are a reporting company and file annual, quarterly and current reports, proxy statements and other information with the SEC. We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the shares of common stock and debt securities we are offering under this prospectus. This prospectus does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities we are offering under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. You may read and copy the registration statement, as well as our reports, proxy statements and other information, at the SEC's public reference rooms at Room 1024, 450 Fifth Street, N.W., Washington, D.C. 20549, as well as at the SEC's regional offices at 500 West Madison Street, Suite 1400, Chicago, IL 60661 and at Seven World Trade Center, New York, NY 10048. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the public reference rooms. Our SEC filings are also available at the SEC's web site at "http://www.sec.gov." In addition, you can read and copy our SEC filings at the office of the National Association of Securities Dealers, Inc at 1735 K Street, N.W., Washington, D.C. 20006.

    The SEC allows us to "incorporate by reference" the information contained in documents that we file with them, which means that we can disclose important information to you by referring to those documents. The information incorporated by reference is considered to be part of this prospectus. Information in this prospectus supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus, while information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below, any filings we will make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934 after the date we filed the registration statement of which this prospectus is a part and before the effective date of the registration statement and any future filings we will make with the SEC under those sections.

    The following documents filed with the SEC are incorporated by reference in this prospectus:

    We will furnish without charge to you, on written or oral request, a copy of any or all of the documents incorporated by reference, including exhibits to these documents. You should direct any requests for documents to Cerus Corporation, Attention: Investor Relations Officer, 2525 Stanwell Drive, Suite 300, Concord, California 94520, telephone: (925) 288-6000.

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PART II

INFORMATION NOT REQUIRED IN THE PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution

    All of the amounts shown are estimates except for the SEC registration fee.

SEC registration fee   $ 75,000
Legal fees and expenses     200,000
Accounting fees and expenses     15,000
Miscellaneous expenses     45,000
   
  Total   $ 335,000
   

Item 15. Indemnification of Directors and Officers

    Under Section 145 of the Delaware General Corporation Law, the Registrant has broad powers to indemnify its directors and officers against liabilities they may incur in such capacities, including liabilities under the Securities Act of 1933, as amended ("Securities Act"). The Registrant's Bylaws also provide that the Registrant will indemnify its directors and executive officers and may indemnify its other officers, employees and other agents to the fullest extent permitted by Delaware law.

    The Registrant's Restated Certificate of Incorporation ("Restated Certificate") provides that the liability of its directors for monetary damages shall be eliminated to the fullest extent permissible under Delaware law. Pursuant to Delaware law, this includes elimination of liability for monetary damages for breach of the directors' fiduciary duty of care to the Registrant and its stockholders. These provisions do not eliminate the directors' duty of care and, in appropriate circumstances, equitable remedies such as injunctive or other forms of non-monetary relief will remain available under Delaware law. In addition, each director will continue to be subject to liability for breach of the director's duty of loyalty to the Registrant, for acts or omissions not in good faith or involving intentional misconduct, for knowing violations of law, for any transaction from which the director derived an improper personal benefit, and for payment of dividends or approval of stock repurchases or redemptions that are unlawful under Delaware law. The provision also does not effect a director's responsibilities under any other laws, such as federal securities laws or state or federal environmental laws.

    The Registrant has entered into agreements with its directors and officers that require Cerus to indemnify such persons to the fullest extent authorized or permitted by the provisions of the Restated Certificate and Delaware law against expenses, judgements, fines, settlements and other amounts actually and responsibly incurred (including expenses of a derivative action) in connection with any proceeding, whether actual or threatened, to which any such person may be made a party by reason of the fact that such person is or was a director, officer, employee or other agent of the Registrant or any of its affiliated enterprise. Delaware law permits such indemnification, provided such person acted in good faith and in a manner such person reasonably believed to be in or not opposed to the best interest of the Registrant and, with respect to any criminal proceeding, had no reasonable cause to believe his or her conduct was unlawful. The indemnification agreements also set forth certain procedures that will apply in the event of a claim for indemnification thereunder.

    At present, there is no pending litigation or proceeding involving a director or officer of the Registrant as to which indemnification is being sought nor is the Registrant aware of any threatened litigation that may result in claims for indemnification by any officer or director.

    The underwriting agreement (Exhibit 1.1) will provide for idemnification by any underwriters of Cerus, our directors, our officers who sign the registration statement and our controlling persons for some liabilities, including liabilities arising under the Securities Act.

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Item 16. Exhibits

Exhibit
Number

  Description of the Document

1.1 * Form of Underwriting Agreement.
3.1 (1) Amended and Restated Certificate of Incorporation.
3.2 (1) Bylaws.
4.1 (1) Specimen Stock Certificate.
4.2   Form of Senior Indenture to be entered into between Cerus and the Trustee.
4.3   Form of Subordinated Indenture to be entered into between Cerus and the Trustee.
4.4 * Form of Senior Note.
4.5 * Form of Subordinated Note.
5.1   Opinion of Cooley Godward LLP.
12.1   Statement Regarding Computation of Ratio of Earnings to Fixed Charges.
23.1   Consent of Ernst & Young LLP, Independent Auditors.
23.2   Consent of Cooley Godward LLP (included in Exhibit 5.1).
24.1   Power of Attorney (see signature page).
25.1   Statement of Eligibility of Trustee under the Senior Indenture.
25.2   Statement of Eligibility of Trustee under the Subordinated Indenture.

*
To be filed by amendment or by a report on Form 8-K pursuant to Section 601 of Regulation S-K and incorporated herein by reference.

(1)
Filed as an exhibit to Cerus' Registration Statement on Form S-1 (No. 333-11341) and incorporated herein by reference.

Item 17. Undertakings

    The undersigned registrant hereby undertakes:

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    Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the SEC this form of indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against these liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by a director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of this issue.

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SIGNATURES

    Pursuant to the requirements of the Securities Act of 1933, as amended, Cerus Corporation certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the city of Concord, state of California, on August 10, 2001.

    CERUS CORPORATION

 

 

By:

 

/s/ 
STEPHEN T. ISAACS   
Stephen T. Isaacs
President and Chief Executive Officer


POWER OF ATTORNEY

    KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below constitutes and appoints STEPHEN T. ISAACS and GREGORY W. SCHAFER, and each or any one of them, his true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for him and in his name, place and stead, in any and all capacities, to sign any and all amendments (including post-effective amendments and registration statements filed pursuant to Rule 462) to this Registration Statement, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission, and to act on and file any supplement to any prospectus included in this registration statement or any such amendment or any subsequent registration statement filed pursuant to Rule 462 under the Securities Act, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming all that said attorneys-in-fact and agents, or any of them, or their or his substitutes or substitute, may lawfully do or cause to be done by virtue hereof.

    Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

Signature
  Title
  Date

 

 

 

 

 
/s/ STEPHEN T. ISAACS   
Stephen T. Isaacs
  President, Chief Executive Officer and Director (Principal Executive Officer)   August 10, 2001

/s/ 
GREGORY W. SCHAFER   
Gregory W. Schafer

 

Vice President, Finance and Chief Financial Officer
(Principal Financial and Accounting Officer)

 

August 10, 2001

/s/ 
B.J. CASSIN   
B.J. Cassin

 

Director

 

August 10, 2001

/s/ 
JOHN E. HEARST   
John E. Hearst

 

Director

 

August 10, 2001


C. Raymond Larkin, Jr.

 

Director

 

August  , 2001

/s/ 
PETER H. MCNERNEY   
Peter H. McNerney

 

Director

 

August 10, 2001

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INDEX TO EXHIBITS

Exhibit
Number

  Description of the Document

1.1 * Form of Underwriting Agreement.
3.1 (1) Amended and Restated Certificate of Incorporation.
3.2 (1) Bylaws.
4.1 (1) Specimen Stock Certificate.
4.2   Form of Senior Indenture to be entered into between Cerus and the Trustee.
4.3   Form of Subordinated Indenture to be entered into between Cerus and the Trustee.
4.4 * Form of Senior Note.
4.5 * Form of Subordinated Note.
5.1   Opinion of Cooley Godward LLP.
12.1   Statement Regarding Computation of Ratio of Earnings to Fixed Charges.
23.1   Consent of Ernst & Young LLP, Independent Auditors.
23.2   Consent of Cooley Godward LLP (included in Exhibit 5.1).
24.1   Power of Attorney (see signature page).
25.1   Statement of Eligibility of Trustee under the Senior Indenture.
25.2   Statement of Eligibility of Trustee under the Subordinated Indenture.

*
To be filed by amendment or by a report on Form 8-K pursuant to Section 601 of Regulation S-K and incorporated herein by reference.

(1)
Filed as an exhibit to Cerus' Registration Statement on Form S-1 (No. 333-11341) and incorporated herein by reference.



QuickLinks

TABLE OF CONTENTS
ABOUT THIS PROSPECTUS
ABOUT CERUS
RISK FACTORS
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS
USE OF PROCEEDS
RATIO OF EARNINGS TO FIXED CHARGES
DESCRIPTION OF DEBT SECURITIES
Global Securities
DESCRIPTION OF CAPITAL STOCK
PLAN OF DISTRIBUTION
LEGAL MATTERS
EXPERTS
WHERE YOU CAN FIND MORE INFORMATION
PART II
SIGNATURES
POWER OF ATTORNEY
INDEX TO EXHIBITS