On October 19, 2026 Havah Therapeutics, Inc. reported to have urged the U.S. Food and Drug Administration to recognize the therapeutic potential of androgen receptor activation in estrogen receptor-positive breast cancer. Backing scientific commentary prepared by its founder, Dr. Stephen Birrell, Havah called for FDA’s evaluation of testosterone in women to reflect published oncology evidence and assess risk by cancer subtype, formulation and clinical exposure.
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Dr. Birrell’s commentary responds to FDA’s September 17 workshop on Testosterone Use in Menopausal Women. Public comments under docket FDA-2026-N-5479 close today.
"The science has advanced, and the regulatory discussion needs to reflect it," said Matthew Brewer, Chief Executive Officer of Havah Therapeutics. "Women need more choices in breast cancer care. With HAV-088 in Phase 2, we are testing whether androgen receptor activation can help women with DCIS control their disease and preserve their breasts."
Research published in Nature Medicine in 2021 demonstrated that androgen receptor activation suppressed tumor growth in estrogen receptor-positive breast cancer models. A 2024 Phase 2 study in The Lancet Oncology reported clinical activity with enobosarm, a different investigational androgen receptor agonist, in advanced disease. These findings support clinical development; they do not establish HAV-088’s efficacy or long-term testosterone safety.
"FDA should evaluate what a specific androgen regimen does in a specific breast cancer subtype," said Dr. Birrell. "The evidence for androgen receptor activation in estrogen receptor-positive disease warrants direct clinical investigation. We need to measure its effects in breast tissue and establish benefit and safety in patients."
Havah supports three priorities outlined by Dr. Birrell:
Assess androgen effects by breast cancer subtype.
Evaluate dose, formulation, delivery route and tissue activity alongside clinical outcomes.
Work with data holders to publish treatment-specific breast and cardiovascular safety outcomes from the historical LibiGel BLISS trial.
Advancing HAV-088 in DCIS
HAV-088 combines testosterone and low-dose anastrozole in an investigational implant designed to deliver approximately three months of therapy. The approach aims to strengthen local androgen signaling: testosterone supplies a precursor for dihydrotestosterone, while low-dose anastrozole is intended to limit competing conversion to estrogen.
HAV-088 is being evaluated in RECAST DCIS (NCT06075953), a randomized Phase 2 platform sponsored by Quantum Leap Healthcare Collaborative. The trial tests whether endocrine therapy and MRI monitoring can help women with hormone receptor-positive ductal carcinoma in situ remain suitable for active surveillance. Surgery remains standard treatment. HAV-088 is not FDA-approved, and its safety and efficacy have not been established.
(Press release, HavaH Therapeutics, OCT 19, 2026, View Source [SID1234673589])