US-based biopharmaceutical firm GTx has started patient enrollment into its Phase II clinical trial of its lead product candidate, enobosarm (GTx-024), for the treatment of women with advanced, androgen receptor positive (AR+), triple negative breast cancer (TNBC).
Enobosarm is also being evaluated in a separate Phase II clinical trial to treat estrogen receptor positive (ER+), AR+ breast cancer, in which patient enrolment was started in September.
The open-label, multi-centre, multinational Phase II trial will evaluate the efficacy and safety of orally administered enobosarm in about 55 women with advanced, AR+ TNBC.
During the trial, they will be given 18mg of enobosarm once daily for up to 12 months and the initial stage will be evaluated among the first 21 evaluable patients.
The company noted that if at least two of 21 patients achieve clinical benefit at week 16, then the trial will proceed to the second stage of enrolment of up to a total of 41 evaluable patients.
GTx executive chairman Robert Wills said: "Most women with triple negative breast cancer have extremely limited treatment options and poor prognoses.
"Based on our preclinical research and positive data from patient-derived and cell line-derived xenografts of TNBC, we are hopeful that enobosarm, by targeting the androgen receptor, may offer another treatment option to women with this disease."
As a result of the trial clinical benefit is defined as a complete response, partial response, or stable disease, as measured by response evaluation criteria in solid tumors (RECIST) at 16 weeks.
Being conducted under the leadership of Dr Hope Rugo from the University of California at San Francisco, the trial will include investigators from over 40 clinical trial sites in the US and abroad.
Enobosarm, a selective androgen receptor modulator (SARM), has been evaluated in multiple completed or ongoing clinical trials enrolling more than 1,500 subjects at doses ranging from 0.1mg to 100mg.
Recently, enobosarm 9mg has been evaluated in a proof of concept Phase II clinical trial of 22 postmenopausal women with ER+ metastatic breast cancer who have previously responded to endocrine therapy.
The trial showed that 17 of the 22 patients were confirmed to be AR+ and six of these 17 patients showed clinical benefit at six months.