GTx, Inc. (NASDAQ: GTXI) today announced positive results from a Phase
2, proof-of-concept, open-label clinical study evaluating enobosarm
(GTx-024), a selective androgen receptor modulator (SARM), for the
treatment of patients with androgen receptor (AR) positive and estrogen
receptor (ER) positive metastatic breast cancer who have previously
responded to hormonal therapy. The clinical data is being presented
today during the Breast Cancer-HER2/ER poster session at the 50th
Annual Meeting of the American Society of Clinical Oncology (ASCO) in
Chicago.
“We know from prior studies and our clinical experience that women with
hormone receptor positive metastatic breast cancer, which has progressed
following treatment with endocrine therapy, often respond to androgen
therapy; yet undesirable side effects, such as facial hair growth and
deepening of the voice, are not acceptable to most patients. Therefore,
alternatives to existing therapies, that are tolerable and effective,
are needed,” said Beth A. Overmoyer, M.D., the principal clinical
investigator in the enobosarm Phase 2 study and director of the
Inflammatory Breast Cancer Program at the Susan F. Smith Center for
Women's Cancers at Dana Farber Cancer Institute, and Assistant Professor
of Medicine at Harvard Medical School. “I find these results to be very
promising given that, in this patient population, achieving stable
disease is considered a success.”
“Based on these encouraging results, we plan to advance the clinical
development of enobosarm in patients with AR and ER positive metastatic
breast cancer,” said Marc S. Hanover, interim CEO, President and COO of
GTx.
Phase 2 Clinical Trial Design and Results
The Phase 2 open-label study is evaluating 22 postmenopausal women with
ER positive metastatic breast cancer, who had previously responded to
adjuvant hormonal therapy for three years or longer, and women diagnosed
with metastatic disease, who had been treated with hormonal therapy for
at least six months, prior to disease progression. Study participants
were heavily pretreated (72.7 percent received previous chemotherapy and
the median number of prior endocrine therapies was 3). The mean time
from initial breast cancer diagnosis is 11 years and the mean age of
patients is 64 years.
Study participants are receiving enobosarm 9 mg once daily until they
display evidence of clinical progression. The primary endpoint is the
proportion of subjects with clinical benefit at 6 months in subjects
with AR+ metastatic lesions. Clinical benefit is defined as those
patients who have either stable disease, a complete response, or a
partial response as defined in the modified RECIST (Response Evaluation
Criteria In Solid Tumors) 1.1 criteria. Upon completion of the study,
clinical benefit response will be correlated with AR status via
metastatic tumor biopsy. Serum prostate specific antigen (PSA) is
evaluated as a biomarker of androgen receptor activity. The study is
being conducted at seven clinical sites in the United States.
Of the 22 patients enrolled in the study, a total of 20 patients had one
or more scheduled assessments for determination of clinical benefit. The
primary endpoint was assessed in 17 AR+ patients with 6 patients
demonstrating clinical benefit at six months, exceeding the pre-defined
statistical threshold requiring that at least 3 of 14 patients with an
AR+ metastatic lesion demonstrate clinical benefit. Additionally,
results showed 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 prostate specific antigen (PSA), which
appears to be an indicator of AR activity. The 6 patients achieving
clinical benefit (35 percent of the 17 patients with AR+ metastatic
lesions) had stable disease. No confirmed complete or partial responses
have been observed in the study. Later this month, the final patient in
the study will have her six month evaluation and three additional
patients continue to demonstrate clinical benefit and remain in the
study. Enobosarm was well tolerated. The most common adverse events
(AEs) reported were pain, fatigue, nausea, hot flash/night sweats, and
arthralgia. The majority of AEs were Grade 1. There were two serious
adverse events (SAEs) reported during the study. Only one of the SAEs,
bone pain of chest cage, was assessed as possibly related to enobosarm.
A copy of the enobosarm poster is available by contacting the Company.
About Breast Cancer and Receptor Status
Breast cancer is the most commonly diagnosed cancer in women and is the
second leading cause of cancer deaths in women in the United States.
Each year, over 200,000 new cases of invasive breast cancer will be
diagnosed in the U.S., and approximately 39,000 women will die from the
disease. Clinical assessment of breast cancer includes routine
characterization of a patient’s receptor status, including the presence
or absence of ER, progesterone receptor and human epidermal growth
factor receptor 2 (HER2) in the tumor tissue. Receptor status is used to
assess the potential for developing metastatic disease, as well as
guiding treatment decisions.
Hormonal manipulation with selective estrogen receptor modulators or
aromatase inhibitors is the standard treatment for patients with tumors
that are ER positive. It is expected that a majority (70-95 percent) of
patients with ER positive breast cancer will also express AR in their
primary tumor samples. High percentages (72-84 percent) of metastatic
breast cancer lesions have been found to be AR positive. In preclinical
and clinical studies, androgens have been shown to suppress breast
cancer growth. In addition, studies have shown that women with
metastatic breast cancer who have been previously treated with tamoxifen
and who progress have responded to nonselective androgens, including
fluoxymesterone, medroxyprogesterone and danazol, with overall response
rates ranging from 20 to 60 percent. However, the unwanted virilizing
side effects of nonselective androgens, including facial and body hair
growth, deepening of the voice box, acne and edema, have limited their
widespread clinical use.
About GTx
GTx, Inc., headquartered in Memphis, Tenn., is a biopharmaceutical
company dedicated to the discovery, development, and commercialization
of small molecules for the treatment of cancer, cancer supportive care,
including prevention and treatment of cancer-related muscle wasting, and
other serious medical conditions.
Forward-Looking Information is Subject to Risk and Uncertainty
This press release contains forward-looking statements based upon GTx's
current expectations. Forward-looking statements involve risks and
uncertainties, and include, but are not limited to, statements relating
to GTx's clinical trials for enobosarm (GTx-024). GTx's actual results
and the timing of events could differ materially from those anticipated
in such forward-looking statements as a result of these risks and
uncertainties, which include, without limitation, the risks (i) that GTx
may not be able to obtain required regulatory approvals to commercialize
its product candidates in a timely manner or at all; or (ii) that
clinical trials being conducted by GTx may not be completed on schedule,
or at all, or may otherwise be suspended or terminated. GTx’s actual
results and the timing of events could differ materially from those
anticipated in such forward-looking statements as a result of these
risks and uncertainties. GTx will continue to need additional funding
and may be unable to raise capital when needed, which would force GTx to
delay, reduce or eliminate its product candidate development programs
and potentially cease operations. You should not place undue reliance on
these forward-looking statements, which apply only as of the date of
this press release. GTx’s quarterly report on Form 10-Q filed with the
Securities and Exchange Commission on May 12, 2014 contains under the
heading, "Risk Factors," a more comprehensive description of these and
other risks to which GTx is subject. GTx expressly disclaims any
obligation or undertaking to release publicly any updates or revisions
to any forward-looking statements contained herein to reflect any change
in its expectations with regard thereto or any change in events,
conditions or circumstances on which any such statements are based.
Copyright Business Wire 2014