Volastra Announces Initial Data from First-in-Human Phase I/II Trial of Novel KIF18A Inhibitor VLS-1488 to be Presented at 2025 ASCO Annual Meeting

-- Novel once-daily oral KIF18A inhibitor demonstrated tumor reduction in 7 of 17 heavily pre-treated advanced ovarian cancer patients enrolled in dose escalation

-- Highly favorable safety profile seen across all tested dose levels and tumor types

--Enrollment in dose expansion is ongoing

Volastra Therapeutics, a clinical-stage cancer biotechnology company focused on chromosomal instability, today announced preliminary safety and efficacy data from its ongoing, first-in-human Phase I/II trial of its novel, oral KIF18A inhibitor, VLS-1488. These results will be featured in an oral presentation at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting on Monday, June 2.

“We are excited by these results from our VLS-1488 KIF18A inhibitor program, demonstrating a favorable safety profile at clinically active doses, with tumor shrinkage in patients with heavily pre-treated ovarian cancer,” said Scott Drutman, M.D., Ph.D., Chief Medical Officer and Head of R&D of Volastra Therapeutics. “These initial data represent a major milestone for the field of chromosomal instability and provide a clear path for dose and patient population selection for the next phase of development.”

As of the January 10, 2025 data cutoff, 52 patients with advanced solid tumors were enrolled to the dose escalation portion of the trial across dose levels ranging from 50 mg to 800 mg. Drug exposures exceeded preclinically-defined efficacious thresholds for anti-tumor activity. No dose limiting toxicities were observed and a maximum tolerated dose was not reached. Less than 45% of patients experienced treatment-related adverse events (TRAEs) of any grade and less than 16% of all patients experienced G3 TRAEs. No patients experienced >G3 TRAEs.

Of the 20 patients with advanced high grade serous ovarian cancer, the majority were platinum resistant and heavily pretreated with a median of 5 prior lines of therapy. At the time of data cutoff, 7 of the 17 response-evaluable patients demonstrated a reduction in tumor size, including 3 Partial Responses per RECIST, with 5 patients remaining on therapy.

“These early data show VLS-1488 to be very well tolerated, with promising initial efficacy in ovarian cancer,” said Ecaterina Dumbrava, M.D., Assistant Professor of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center and investigator on the trial. “The data that will be presented demonstrate the potential of KIF18A as a novel, relevant therapeutic target for hard-to-treat cancers and I look forward to continued development.”

Volastra continues to enroll patients in this study and explore the broad potential of its two KIF18A inhibitors, VLS-1488 and sovilnesib in ovarian and other cancers.

Details of the ASCO Rapid Oral Abstract Session are as follows:

Title: Preliminary results from a first-in-human, phase I/II study of VLS-1488, an oral KIF18A inhibitor, in patients with advanced solid tumors

Presenter: Ecaterina Dumbrava, M.D., Assistant Professor of Investigational Cancer Therapeutics, The University of Texas MD Anderson Cancer Center

Session Title: Developmental Therapeutics—Molecularly Targeted Agents and Tumor Biology – Small Molecules

Session Date and Time: Monday, June 2, 2025, 8:00 AM- 9:30 AM CT

Location: McCormick Place Convention Center, S406

About VLS-1488

VLS-1488 is a novel, oral small molecule inhibitor of KIF18A, a kinesin protein essential for cancer cell division and a synthetic lethal target in chromosomally unstable cancers. VLS-1488 was granted Fast Track Designation from the FDA in October 2024 for the treatment of patients with platinum-resistant high-grade serous ovarian cancer.

About VLS-1488-2201 Trial (NCT05902988)

The Phase 1/2 trial is evaluating the safety, tolerability, PK, and antitumor activity of VLS-1488 in patients with advanced solid tumors, including high grade serious ovarian cancer. The study consists of two parts, Dose Escalation and Dose Expansion. Enrollment to the dose expansion portion of this study is ongoing.

About Ovarian Cancer and Chromosomal Instability

In the U.S. alone, there are more than 20,000 new cases of ovarian cancer each year, over 75% of which are advanced. Most of these patients will experience disease progression on platinum-based therapy.

High grade serous ovarian cancer accounts for approximately 75% of all ovarian cancers, about 80% of all deaths and is almost universally chromosomally unstable.

About Volastra Therapeutics

Volastra Therapeutics is a clinical-stage biotechnology company pioneering novel approaches to the treatment of cancer by targeting chromosomal instability. The company leads the field with two differentiated, oral KIF18A inhibitors, VLS-1488 and sovilnesib (formerly AMG-650). Both assets are currently being evaluated in Phase 1 clinical trials for platinum resistant ovarian cancer and other advanced solid tumors. Volastra is also developing new techniques to understand the biology of chromosomal instability and leveraging these insights to drive forward a preclinical pipeline of therapies against innovative targets. Volastra was founded in 2019 by Lewis Cantley, Ph.D., Samuel Bakhoum, M.D., Ph.D., and Olivier Elemento, Ph.D., and is funded by key investors including Polaris Partners, ARCH Ventures, B-Capital, Droia Ventures, Vida Ventures, Catalio Capital Management and Eli Lilly & Company. Notable partners include Tailor Bio and Microsoft.

For more information, please visit www.volastratx.com.

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