Aviva Biopharm Inc. Unveils Groundbreaking Pre-Clinical Data on d3-T, a First-in-Class Testosterone Therapy for Women at ENDO 2025

d3-T is a Novel, Non-Aromatizing Androgen, Offering the Benefits of Testosterone Without Converting to Estradiol Addressing a Known Breast Cancer Risk

CONCORD, Mass.--(BUSINESS WIRE)--Aviva Biopharm Inc. (Aviva Bio), a clinical-stage biopharmaceutical company developing next-generation hormone therapies for women, announced today that new preclinical data on its lead compound, d3-testosterone (d3-T), was presented at ENDO 2025, the Endocrine Society’s flagship annual meeting, on July 14th in San Francisco.

The poster, titled “Characterization of d3-Testosterone, A Novel, Non-Aromatizing Androgen,” will be presented by Judith Boice, PhD, CEO of Aviva Bio and co-author of the research.

“d3-T shares all the characteristics of testosterone, but is re-engineered for safety,” said Judith Boice, PhD, CEO of Aviva Bio. “d3-T is a novel, structurally identical form of testosterone where select hydrogen molecules have been substituted with deuterium. This small change creates a significant breakthrough.”

Unlike conventional testosterone, d3-T resists aromatization, the metabolic process that converts androgens into estradiol. This resistance may significantly reduce the risk of estradiol-driven side effects such as breast cancer and gynecomastia, making d3-T a potentially transformative therapy for patients.

“This is a pivotal moment addressing a significant unmet need in women’s health,” said Barbara S. Levy, MD, FACOG, FACS, Chief Medical Officer, Visana Health Inc. and Clinical Professor, Obstetrics and Gynecology, The George Washington University School of Medicine and Health Sciences. “d3-T could significantly enhance options for hormone therapy in menopausal and perimenopausal women.”

Key findings from the preclinical study include:

• d3-T is highly resistant to aromatization, as demonstrated by multiple studies in the presence of pure, concentrated aromatase
• d3-T is equally potent and efficacious to testosterone in inducing androgen receptor activation
• d3-T has similar metabolic stability and metabolite production compared with testosterone in both human and rat liver cells
• These data support advancing d3-T into clinical trials

d3-T may be a useful alternative in clinical situations where the aromatization of testosterone limits its therapeutic potential. This safety challenge has hampered prior efforts to gain FDA approval of a testosterone product for women. d3-T addresses this challenge and holds promise for broader indications including low libido and muscle loss associated with aging and GLP-1 agonist use.

Aviva Bio holds exclusive rights to d3-T and is preparing to initiate a Phase I clinical trial in early 2026.

About Aviva Bio

Aviva Bio is a clinical-stage biotechnology company unlocking the full potential of hormone-based medicine. Through novel drug design and a focus on unmet needs in women’s health, Aviva Bio is developing first-in-class therapeutics to improve lives. It’s lead program, AVA-291 (d3-Testosterone), is on track to become the first FDA-approved testosterone therapy designed for women.

About AVA-291 (d3-Testosterone)

AVA-291 or d3-testosterone (d3-T) is a structurally identical, deuterium-substituted isotopologue of testosterone designed to resist aromatization to estradiol. Conversion of testosterone into estradiol is linked with potential safety (breast cancer) and tolerability (gynecomastia) concerns associated with testosterone therapy. In vitro studies of d3-T have demonstrated a similar metabolic profile and similar androgen receptor affinity as testosterone, but unlike testosterone it is highly resistant to aromatization to estradiol. d3-T may be a useful alternative to testosterone in clinical situations where the aromatization of testosterone limits its therapeutic potential, such as hormone replacement therapy in postmenopausal women, addressing muscle wasting in patients on GLP-1 therapy, the treatment of ER+ breast cancer, or in men on testosterone therapy who develop gynecomastia.