General Description

Kyzatrex (testosterone undecanoate) is a proprietary softgel oral formulation of testosterone, an androgen. 

Kyzatrex is specifically indicated for testosterone replacement therapy in adult males for conditions associated with a deficiency or absence of endogenous testosterone.

Kyzatrex is supplied as a softgel capsule for oral administration. 

Prior to initiating Kyzatrex, confirm the diagnosis of hypogonadism by ensuring that serum testosterone concentrations have been measured in the morning on at least two separate days and that these concentrations are below the normal range. Kyzatrex should be administered with food.

• Starting dosage: 200 mg orally once in the morning and once in the evening
• Adjust the dosage to a minimum of 100 mg once in the morning and a maximum of 400 mg twice daily based on serum testosterone drawn 3 to 5 hours after the morning dose at least 7 days after starting treatment or following dose adjustment and periodically thereafter.

Mechanism of Action

Kyzatrex (testosterone undecanoate) is an oral formulation of testosterone, an endogenous androgen. Testosterone and dihydrotestosterone (DHT), are responsible for the normal growth and development of the male sex organs and for maintenance of secondary sex characteristics. These effects include the growth and maturation of prostate, seminal vesicles, penis, and scrotum; the development of male hair distribution, such as facial, pubic, chest, and axillary hair; laryngeal enlargement; vocal cord thickening; alterations in body musculature; and fat distribution. Male hypogonadism, a clinical syndrome resulting from insufficient secretion of testosterone, has two main etiologies. Primary hypogonadism is caused by defects of the gonads, such as Klinefelter syndrome or Leydig cell aplasia, whereas secondary hypogonadism (also known as hypogonadotropic hypogonadism) is the failure of the hypothalamus (or pituitary gland) to produce sufficient gonadotropins (FSH, LH).

Side Effects

The most frequent adverse effect associated with the use of Kyzatrex was hypertension.

Clinical Trial Results

The FDA approval of Kyzatrex was based on efficacy data from Study MRS-TU-2019EXT, a multi-center, open-label study of approximately 6 months of duration in 139 hypogonadal males. Patients received Kyzatrex at a starting dose of 200 mg twice daily with meals. The dosage was adjusted on Days 28 and 56 between a minimum dose of 100 mg (single morning dose) and a maximum dose of 800 mg (400 mg twice daily) based on plasma testosterone concentration from a single blood draw between 3 to 5 hours after the morning dose . The primary efficacy endpoint was the percentage of Kyzatrex-treated patients with mean plasma total testosterone concentration (Cavg) over 24-hours within the normal range of 222-800 ng/dL on the final PK visit of the study at Day 90. This endpoint was reached by 88% of participants. Secondary endpoints were also reached: The percentage of patients who received KYZATREX and had testosterone Cmax threshold less than or equal to 1200 ng/dL, between 1440 and 2000 ng/dL, and greater than 2000 ng/dL at the final PK visit were 88%, 4%, and 0%, respectively.