Trial to assess testosterone undecanoate in older men with hypogonadism

Marius Pharmaceuticals has initiated a post-marketing study to support potential label expansion of testosterone undecanoate (Kyzatrex) CIII capsules in men aged 65 to 80 with hypogonadism, the company announced in a news release.¹

The open-label, single-site study plans to enroll 50 men who will be assessed over a 6-month time period. The investigators will evaluate changes in overall quality of life and in key health markers related to aging, such as cardiovascular parameters, body composition, strength-related measures, and inflammation. With these end points, the investigators are hoping to better understand how treatment with testosterone undecanoate “may support health measures that meaningfully affect day-to-day function and long-term outcomes” in older men.

The study is also comparing testosterone undecanoate’s labeled titration protocol with a simplified once-daily dosing regimen. According to Marius, a simplified regimen, if effective, may be especially beneficial for an older population of men.

“Marius is committed to advancing the understanding of men’s health across all ages, and this study reflects our interest in evaluating outcomes that matter most to older patients,” said Om Dhingra, PhD, Chief Scientific Advisor and Board Director at Marius, in the news release from the company.¹ “By focusing on cardiovascular markers, body composition, strength, and inflammation, we hope to generate insights that can help clinicians care for this growing patient population.”

About testosterone undecanoate

Testosterone undecanoate is currently approved for adult males with conditions associated with a deficiency or absence of endogenous testosterone. The initial approval of the capsules was based on a multi-center phase 3 trial in 155 men aged 18 to 65 years. All patients had confirmed hypogonadism, defined as a serum testosterone level below the normal level (281 ng/dL or lower) and at least 1 sign or symptom of testosterone deficiency.

Overall, the study achieved its primary end point, showing that 88% of efficacy-evaluable patients (n = 139) achieved a mean plasma total testosterone concentration (Cavg) over 24 hours within the normal range (222 to 800 ng/dL) at day 90, the final pharmacokinetic visit in the study. Patients who received testosterone undecanoate also reported improvements in symptoms of low testosterone such as quality of life, energy/fatigue, erectile function, sexual intercourse, and mood. 

The most common adverse event (2% or greater of patients) in the testosterone undecanoate arm was increased blood pressure, reported in 2.6% of patients.

REFERENCE

1. Marius Pharmaceuticals to initiate study evaluating KYZATREX® (testosterone undecanoate) CIII capsules in men ages 65–80. News release. Marius Pharmaceuticals LLC. January 8, 2026. Accessed January 9, 2026. https://mariuspharma.com/news/marius-pharmaceuticals-to-initiate-study-evaluating-kyzatrex-testosterone-undecanoate-ciii-capsules-in-men-ages-65-80/