Context Therapeutics and SOLTI launch ONAWA: a Window of Opportunity Study in Breast Cancer with Apristor

In Clinical Studies News by Barbara Jacoby

Source: Business Wire


Context Therapeutics, a clinical-stage biopharmaceutical company dedicated to advancing medicines for hormone driven cancers, today announced a clinical collaboration with SOLTI, a leading collaborative and academic group in Spain dedicated to clinical and translational research in breast cancer. This clinical collaboration, being supported by Context and sponsored by SOLTI, is a window of opportunity study (WOO) in the neoadjuvant setting for breast cancer.

During the study, patients participating in the ONAWA ( ONA pristone W indow A ssessment) trial will receive oral doses of the progesterone receptor antagonist, Apristor ® (onapristone ER). Patients will be biopsied on day one, followed immediately by treatment and a final biopsy after three weeks, on the day of their full lumpectomy or mastectomy. Data generated from this study is intended to confirm the Recommended Phase 2 Dose (RP2D) of Apristor and to provide comprehensive biomarker data to further validate that the antitumor activity of Apristor is driven through downregulation of progesterone receptor and associated signaling pathways. This data will support Context’s ongoing and planned Phase 2 studies in breast, ovarian, and endometrial cancers.

“We are thrilled to enter into this collaboration with SOLTI and facilitate this window of opportunity study. We expect that this study will provide additional biomarker data to support our planned Phase 2 studies in progesterone receptor positive (PR+) female cancers,” said Martin Lehr, CEO of Context Therapeutics.

The study, conducted within SOLTI’s network, has two Principal Investigators, both members of SOLTI Governing Board: Dr. Meritxell Bellet, Senior Consultant at Breast Cancer Unit at Vall d’Hebron University Hospital and Dr. Cristina Saura, Head of Breast Cancer Unit at Vall d’Hebron University Hospital. “The majority of breast cancer patients have an hormone-dependent disease. The hormones estrogen and progesterone drive breast cancer progression in those patients, but antiestrogens are the only antihormonal therapy available to clinicians. As such, antiestrogen resistance is now a major clinical challenge,” said Dr. Bellet. “We believe that a progesterone receptor antagonist has the potential to address antiestrogen resistance and/or potentiate antiestrogen activity, which we believe will lead to better outcomes for patients. This window of opportunity provides us with the first clinical opportunity to delve deep into how progesterone receptor antagonists modulate the breast cancer tumor and its microenvironment.”

About Hormone Driven Breast Cancer

Hormone receptor positive (HR+) breast cancer is the most common form of breast cancer and accounts for more than 70% of all breast cancers. HR+ cancer is usually treated with antiestrogen therapies first that help stop tumor growth. For many patients, antiestrogen therapy becomes ineffective over time and the cancer becomes resistant to antiestrogen therapy. In this recurrent setting, progesterone receptor has emerged as a prominent resistance mechanism. It is estimated that there are over 750,000 patients with recurrent disease worldwide.

About Window of Opportunity Trials

Window of opportunity (WoO) trials take advantage of natural scheduling delays that occur between initial consultation and surgery. This allows learning about anticancer activity of the intervention in a patient who has not been exposed to previous therapies. Such studies can better define biological effects of the therapy and outline the target patient population for the following studies. In turn, development and identification of promising drugs could speed up. WoO trials are usually short, in the order of 2–6 weeks of treatment, making it difficult to achieve clinical endpoints such as objective response. The endpoint of WoO trial is usually biomarker modulation. The collection of before and after treatment tumor biopsies allows determination of extent of target inhibition, cell proliferation and apoptosis, and identification of other biomarkers.

About Apristor

Apristor (onapristone 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 PR+ cancers. Preliminary preclinical and clinical data suggest that Apristor has anticancer activity by inhibiting the binding of progesterone receptor to chromatin, downregulating cancer stem cell mobilization, and blocking immune evasion. Apristor is an investigational drug that has not been approved for marketing by any regulatory authority.


SOLTI is a non-profit academic research association with more than 20 years of experience in conducting innovative clinical and translational research. The organization’s goal is to address unmet medical needs in breast cancer that help us to answer questions of major scientific interest and relevance in the field of oncology. SOLTI has a network of more than 300 professionals distributed in over 90 hospitals in Spain, Portugal, France and Italy. For more information, please visit:

About Context Therapeutics

Context is a clinical-stage biopharmaceutical company advancing medicines to treat hormone driven cancers. Context’s lead program is Apristor, an investigational Phase 2 drug that is being developed for progesterone receptor positive (PR+) metastatic breast, ovarian, and endometrial cancers. For more information on Context, visit