PHILADELPHIA--(BUSINESS WIRE)--Context Therapeutics LLC, a clinical-stage biopharmaceutical company dedicated to advancing medicines for hormone driven cancers, today announced that results from a safety review from preclinical and two Phase 1-2 studies evaluating its drug candidate onapristone extended release (ONA-ER) for the treatment of progesterone receptor (PR) positive cancers has been published in the journal Drug Safety. ONA-ER is an investigational, potentially best-in-class oral progesterone receptor (PR) antagonist. If approved, ONA-ER would be the first FDA-approved medication for PR+ cancers.

Antiprogestins demonstrated promising activity against breast and gynecological cancers, but liver-related safety concerns limited the advancement of this therapeutic class. Onapristone was previously evaluated in Phase 2 studies for metastatic breast cancer. Due to liver enzyme elevations identified during these studies, further development was halted. Evaluation of antiprogestin pharmacology and pharmacokinetic (PK) data suggests that liver enzyme elevations might be related to off-target effects associated with serum Cmax levels. If correct, this suggests the use of pharmaceutic strategies targeting efficacious systemic dose levels, but with a diminished Cmax. One such strategy twice-daily dosing of an extended release (ER) formulation of onapristone (ONA-ER) was developed and clinically evaluated in two phase 1-2 studies in PR-positive malignancies. In light of renewed interest in antiprogestin therapy for treating PR-positive breast and gynecologic cancer, the publication authors assessed the hepatotoxic potential of: (a) onapristone in liver-focused preclinical toxicology models, and (b) ONA-ER based on data from two phase 1-2 studies involving breast, ovarian, endometrial, and prostate cancer patients.

These results suggest that the extended-release formulation by reducing drug exposure may be associated with a reduced risk of hepatotoxicity, and supports the continued clinical evaluation of ONA-ER for treating PR-positive cancers, said study author James H. Lewis, MD, Director of Hepatology at MedStar Georgetown University Hospital.

In the Phase 1-2 trials, ONA-ER at escalating doses of 10 mg to 50 mg twice-a-day had a favorable safety and tolerability profile at all doses. There were no treatment-related severe adverse events among patients treated with ONA-ER. No clinical trial subject receiving ONA-ER developed liver test elevations meeting Hys Law criteria or other clinically significant hepatic injury considered to be drug-related.

Poor tolerability has limited the potential of antiprogestins for cancer patients, said Martin Lehr, Chief Executive Officer of Context. We are pleased with the results from this review, which highlight the potential of ONA-ER to meet a significant unmet need for a well tolerated treatment for PR-positive cancers.

About Onapristone ER

Onapristone ER (extended release) is a potent and specific antagonist of the progesterone receptor that is orally administered. Currently, there are no approved therapies that selectively target progesterone receptor (PR) positive cancers. Preclinical and clinical data suggest that onapristone ER has anticancer activity by inhibiting progesterone receptor binding to chromatin, downregulating cancer stem cell mobilization and blocking immune evasion. Onapristone ER is currently being evaluated in patients with PR+ rare ovarian and endometrial cancers in the ongoing Phase 2 ONWARD 220 clinical trial. Additional Phase 2 clinical trials in ER+, PR+, HER2- breast cancer and PR-positive endometrial cancers will be initiated in 2020. Onapristone ER is an investigational drug that has not been approved for marketing by any regulatory authority.

About Context Therapeutics

Context Therapeutics LLC is a clinical-stage biopharmaceutical company advancing medicines to treat hormone driven cancers. Contexts lead program is onapristone ER, an investigational Phase 2 drug that is being developed for progesterone receptor positive breast, ovarian and endometrial cancers. For more information on Context, visit http://www.contexttherapeutics.com.

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Context Therapeutics Announces Publication of Onapristone Extended Release Safety Review Results - Business Wire