GTx enrolls first patient in Phase 2 clinical trial of enobosarm in ER+/AR+ breast cancer

Enobosarm, a selective androgen receptor modulator (SARM), is the Company’s lead product candidate.

GTx executive chairman Robert Wills said: "Additional endocrine directed therapies are needed for the treatment of estrogen receptor positive breast cancer as many women who respond to hormonally directed therapy will continue to demonstrate response with subsequent hormonal manipulation.

"We believe that enobosarm may provide a new hormonal approach for the treatment of estrogen receptor positive breast cancer and may delay the need for chemotherapy in these women."

The open-label, multi-center, multinational Phase 2 clinical trial (NCT02463032) will assess the efficacy and safety of orally administered enobosarm in up to 88 evaluable patients with metastatic or locally advanced, ER+/AR+ breast cancer. Patients will receive either enobosarm 9 mg or 18 mg given daily for up to 24 months.

The initial stage of evaluation will be assessed among the first 18 evaluable patients for each dosing arm. If at least 3 of 18 patients achieve clinical benefit at week 24, then the trial will proceed to the second stage of enrollment for that dosing arm to assess clinical benefit in a total of 44 evaluable patients per arm.

Clinical benefit is defined as a complete response, partial response, or stable disease, as measured by Response Evaluation Criteria in Solid Tumors (RECIST) at 24 weeks. The lead investigator for the trial is Dr. Beth Overmoyer from the Dana Farber Cancer Institute and the Harvard Medical School.

About enobosarm

Enobosarm, a selective androgen receptor modulator (SARM), has been evaluated in 23 completed or ongoing clinical trials enrolling over 1,500 subjects at doses ranging from 0.1 mg to 100 mg. At all evaluated dose levels, enobosarm was observed to be generally safe and well tolerated.

Most recently, enobosarm 9 mg has been tested in a Phase 2, proof of concept clinical trial of 22 postmenopausal women with ER+ metastatic breast cancer who have previously responded to endocrine therapy. Seventeen of the 22 patients were confirmed to be AR+. Six of these 17 patients demonstrated clinical benefit at six months. Seven patients in total (one patient with indeterminate AR status) achieved clinical benefit at six months.

The results also demonstrated that, after a median duration on study of 81 days, 41 percent of all patients (9/22) achieved clinical benefit as best response and also had increased PSA which appears to be an indicator of AR activity. Enobosarm was well tolerated. The most common adverse events reported were pain, fatigue, nausea, hot flash/night sweats, and arthralgia.