Phase 2 Trial of Tomivosertib Begins Dosing Advanced Castration-resistant PC Patients

Phase 2 Trial of Tomivosertib Begins Dosing Advanced Castration-resistant PC Patients

A Phase 2 clinical trial evaluating eFFECTOR Therapeutics’ investigational therapy tomivosertib (eFT508), for men with advanced castrate-resistant prostate cancer (CRPC) who failed to respond to androgen receptor signaling (ARS) inhibitors, has begun dosing patients.

The trial (NCT03690141), currently recruiting participants, will evaluate the safety, tolerability and antitumor activity of tomivosertib in patients whose disease progressed while on treatment with the ARS inhibitors Zytiga (abiraterone acetate) or Xtandi (enzalutamide).

Thirty patients will be enrolled across 10 clinical sites in the U.S. Participants will receive oral capsules of tomivosertib, administered twice a day for 52 weeks.

The study primarily aims to assess tomivosertib’s anti-tumor response, defined by either a 50 percent or larger reduction in prostate-specific antigen (PSA) levels, or objective response measured by iRECIST, a response evaluation criteria for solid tumors, with interim and final analyses at eight and 12 months after the last patient commenced treatment.

Secondary measures include time to disease progression or death, overall survival, and safety. The behavior of tomivosertib once inside the body — absorption, metabolism, excretion — also will be assessed.

In previous clinical trials, tomivosertib was found safe, well-tolerated, and with a long-term anti-tumor activity in patients with solid tumors or lymphomas whose disease progressed after multiple treatments.

“Tomivosertib is highly active in preclinical models of prostate cancer, including castrate-resistant xenografts and explant models derived directly from patients’ tumor samples,” Steve Worland, PhD, president and CEO of eFFECTOR, said in a press release.

Tomivosertib is a potent, highly selective, oral inhibitor of two kinases, MNK1 and MNK2, known for promoting tumor growth and its ability to evade the immune system. The treatment also seems to have a direct action in some cancers, including prostate cancer.

“Tomivosertib may therefore provide a new way to address treatment-resistant prostate cancers, including those which are driven by variant forms of the androgen receptor,” Worland said.

Tomivosertib also is being tested in two additional Phase 2 trials, one as an add-on therapy for patients with solid tumors who failed approved immunotherapies (NCT03616834) and another in combination with Bavencio (avelumab) for patients with hard-to-treat microsatellite stable colorectal cancer (NCT03258398).

It also will be tested in combination with Keytruda (pembrolizumab) in triple negative breast cancer.