Aviva to advance, announce new data for AVA-291 women's testosterone therapy

Aviva Bio announced it has received formal feedback from the US Food and Drug Administration (FDA) following a Type B meeting regarding development requirements for AVA-291 (d3-testosterone), a next-generation testosterone therapy designed specifically for women. The company said the feedback marks an important milestone for a field that has long faced safety concerns and a lack of FDA-approved, female-specific testosterone therapies, particularly related to breast cancer risk associated with aromatization.¹

Concerns about testosterone in women

Testosterone therapy in women has historically relied on repurposed formulations developed for men, despite known biological and safety differences. A central concern has been aromatization, the conversion of testosterone to estrogen in tissues such as the breast, which has been linked to increased breast cancer risk and has limited broader clinical development.

According to Aviva Bio, the FDA acknowledged this potential risk during the Type B meeting, reinforcing its relevance as a core regulatory and safety issue. The company said the agency’s feedback reflects alignment around the need for therapies designed with molecular features that address aromatization directly, rather than relying solely on dosing or formulation strategies.

“For decades, testosterone therapy for women has depended on repurposed male formulations, rather than drugs designed with women’s biology and safety considerations in mind,” said Judith A. Boice, PhD, chief executive officer of Aviva Bio. “Our FDA feedback reinforces the need for a new standard—one anchored in safety, enabled by molecular precision, and developed with regulatory clarity from the start.”

AVA-291 data accepted for AACR

To further support AVA-291’s differentiated profile, Aviva Bio announced that new preclinical data have been accepted for presentation at the American Association for Cancer Research (AACR) Annual Meeting in April 2026. The company said the data show that AVA-291 has approximately 1000-fold less potential to stimulate breast cancer cell proliferation compared with ordinary testosterone.

“The data we are presenting at AACR provides mechanistic evidence that AVA-291 (d3-T) has a reduced risk of exacerbating breast cancer compared with ordinary T,” said Bradford C. Sippy, chief technology officer of Aviva Bio. “This builds on our prior work showing that AVA-291 is resistant to aromatization and highlights the potential clinically differentiated profile.”

AVA-291 is a deuterium-substituted isotopologue of testosterone that is structurally identical to ordinary testosterone but engineered to resist aromatization. In vitro studies have shown similar androgen receptor affinity and metabolic profiles compared with testosterone, while human clinical studies suggest d3-testosterone can function as a direct substitute for standard testosterone therapies.

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In a previous announcement from Aviva regarding pre-clinical data of d3-T, Barbara S. Levy, MD, FACOG, FACS, Chief Medical Officer, Visana Health Inc; clinical professor, Obstetrics and Gynecology, The George Washington University School of Medicine and Health Sciences, stated, “This is a pivotal moment addressing a significant unmet need in women’s health. d3-T could significantly enhance options for hormone therapy in menopausal and perimenopausal women.”²

Broader development potential

Aviva Bio is advancing AVA-291 as part of a broader development program across multiple women’s and men’s health indications where androgen signaling is clinically meaningful but constrained by aromatization-related safety or tolerability concerns. Potential applications cited by the company include hormone replacement therapy in menopausal women, gynecomastia in men receiving testosterone therapy, muscle loss or low libido in patients receiving GLP-1 therapies, and estrogen receptor–positive breast cancer.¹

The company said it remains focused on translating FDA guidance and emerging mechanistic data into a disciplined clinical and regulatory development program, while also evaluating strategic collaborations to support future clinical, regulatory, and commercial progress. AVA-291 is protected by multiple issued US patents extending to at least 2041.

References:

1. Aviva Bio announces FDA guidance on development pathway for women’s testosterone therapy and new evidence of a reduced risk of breast cancer cell proliferation for AVA-291. Aviva Bio. Press release. January 26, 2026. Accessed January 26, 2026. https://www.businesswire.com/news/home/20260126103179/en/Aviva-Bio-Announces-FDA-Guidance-on-Development-Pathway-for-Womens-Testosterone-Therapy-and-New-Evidence-of-a-Reduced-Risk-of-Breast-Cancer-Cell-Proliferation-for-AVA-291
2. Aviva Biopharm Inc. unveils groundbreaking pre-clinical data on d3-T, a first-in-class testosterone therapy for women at ENDO 2025. Aviva Bio. Press release. July 14, 2025. Accessed January 26, 2026. https://www.businesswire.com/news/home/20250714405897/en/Aviva-Biopharm-Inc.-Unveils-Groundbreaking-Pre-Clinical-Data-on-d3-T-a-First-in-Class-Testosterone-Therapy-for-Women-at-ENDO-2025