Jatenzo Safety Signals and FDA Actions

How Jatenzo Works and Why Its Safety Profile Differs

Jatenzo delivers testosterone undecanoate through a self-emulsifying drug delivery system (SEDDS) that promotes absorption via the intestinal lymphatic system rather than portal hepatic circulation [1]. This matters for safety. Older oral androgens like methyltestosterone passed through the liver on first pass, causing hepatotoxicity, cholestatic jaundice, and peliosis hepatis. By bypassing portal circulation, Jatenzo avoids those first-pass hepatic insults [2].

The lymphatic route does not eliminate all safety concerns. It introduces a different pharmacokinetic profile with higher peak-to-trough variability than injectable or transdermal formulations. Patients must take Jatenzo twice daily with food containing at least 20 grams of fat to achieve adequate absorption [1]. Skipping meals or eating low-fat meals drops bioavailability significantly, creating inconsistent serum testosterone levels that complicate both efficacy assessment and adverse-event attribution.

The twice-daily dosing requirement also means that drug exposure tracks with dietary compliance, not just adherence to pill-taking. This pharmacokinetic reality shaped how the FDA evaluated Jatenzo's safety data, because blood pressure readings and hematocrit values in clinical trials reflected a population that followed specific dietary instructions under trial conditions.

The FDA Advisory Committee Vote and Initial Approval

The FDA's Bone, Reproductive and Urologic Drugs Advisory Committee reviewed Jatenzo on April 27, 2018. The vote was tight. The committee voted 15 to 13 that the benefits outweighed the risks, but several members expressed concern about cardiovascular signals and the lack of long-term outcome data [3].

Dr. Daniel Fabricant, a committee member, noted that "the blood pressure signal is not trivial in a population already at elevated cardiovascular risk" [3]. The FDA's own review division flagged that men with hypogonadism often carry comorbidities including obesity, type 2 diabetes, and dyslipidemia, meaning even modest blood pressure increases could compound existing risk.

The FDA ultimately approved Jatenzo on March 27, 2019, with conditions. The agency required a Risk Evaluation and Mitigation Strategy (REMS) and mandated that the label include warnings about blood pressure elevation and polycythemia [4]. This was the first oral testosterone product approved in the United States, and the FDA treated the novelty of the delivery route as reason for additional caution rather than reduced scrutiny.

Blood Pressure Elevation: The Primary Cardiovascular Signal at Approval

Blood pressure increase was the most debated safety finding in Jatenzo's preapproval data. In the key trial by Swerdloff et al. (N=166), 87% of patients achieved eugonadal testosterone levels (300 to 1 to 100 ng/dL) at the 3-month primary endpoint [1]. But the same trial recorded mean systolic blood pressure increases of 3 to 5 mmHg in the Jatenzo arm compared to a topical testosterone gel comparator.

Five percent of Jatenzo-treated patients developed new-onset hypertension (systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg) during the trial, compared to 2% on topical testosterone [1]. While the absolute numbers were small, the direction of the signal was consistent across subgroup analyses.

A longer-term extension study (N=315 to 12 months) confirmed the persistence of this blood pressure effect [5]. The mean systolic increase did not resolve over time, suggesting this is a sustained pharmacologic effect rather than an early adaptation. The Endocrine Society's 2018 clinical practice guideline on testosterone therapy already recommended blood pressure monitoring for all testosterone formulations, but the Jatenzo label goes further, specifying measurement at every clinic visit [6].

The mechanism likely involves testosterone-mediated sodium and water retention, compounded by Jatenzo's peak-to-trough swings. Unlike steady-state transdermal delivery, twice-daily oral dosing produces supraphysiologic peaks that may activate mineralocorticoid pathways more aggressively.

Polycythemia and Hematocrit: A Dose-Dependent Risk

Polycythemia (hematocrit >54%) is the most common laboratory abnormality with testosterone replacement therapy across all formulations. Jatenzo is no exception. In the key trial, 4.8% of patients developed hematocrit values exceeding 54%, and dose reductions resolved the elevation in all cases [1].

The Jatenzo label specifies hematocrit measurement at baseline, at 3 months, at 6 months, and annually thereafter [4]. If hematocrit exceeds 54%, the prescribing information directs clinicians to stop the drug until hematocrit falls below 50%, then restart at a lower dose. This is stricter than some injectable testosterone labels, which set the threshold at 55%.

A pooled analysis of testosterone formulations published in the Journal of Clinical Endocrinology and Metabolism found that polycythemia risk correlates with peak serum testosterone levels rather than trough levels [7]. Because Jatenzo's oral SEDDS formulation produces relatively high peak concentrations (Cmax values averaging 800 to 1 to 200 ng/dL depending on dose and meal fat content), the polycythemia signal tracks with the drug's pharmacokinetic profile [1].

The clinical significance of testosterone-induced polycythemia remains debated. Retrospective data suggest that hematocrit values above 54% increase venous thromboembolism risk, but prospective evidence quantifying that risk specifically in testosterone-treated men is limited [8].

Hepatic Safety: Better Than Legacy Oral Androgens, Not Risk-Free

Jatenzo's lymphatic absorption pathway largely eliminates the hepatotoxicity concerns that doomed earlier oral androgens like methyltestosterone and fluoxymesterone. In the 12-month extension study, no cases of drug-induced liver injury, peliosis hepatis, or hepatic tumors were reported [5]. Liver transaminase elevations occurred in 2.1% of patients, all grade 1 (less than 3 times the upper limit of normal), and all resolved without treatment discontinuation [5].

This is a meaningful safety advantage. The FDA's 2004 guidance on testosterone products specifically cited hepatotoxicity as a concern with oral formulations, which is one reason the United States had no approved oral testosterone for decades while oral testosterone undecanoate (Andriol) was available in Europe and Canada [9].

The FDA still requires liver function monitoring on the Jatenzo label, recommending baseline and periodic assessment, though no specific interval is mandated beyond clinical judgment [4]. The distinction between Jatenzo's hepatic safety profile and that of 17-alpha-alkylated androgens should be made explicit to patients who may have encountered warnings about "oral testosterone" causing liver damage.

The TRAVERSE Trial and the Class-Wide Boxed Warning

The TRAVERSE trial (Testosterone Replacement Therapy for Assessment of Long-Term Vascular Events and Efficacy Response in Hypogonadal Men) published in the New England Journal of Medicine in June 2023 was a landmark study [10]. It randomized 5,204 men aged 45 to 80 with hypogonadism and established or high risk for cardiovascular disease to transdermal testosterone gel or placebo and followed them for a median of 33 months.

The primary MACE endpoint (cardiovascular death, nonfatal MI, nonfatal stroke) occurred in 7.0% of the testosterone group versus 7.3% of the placebo group (hazard ratio 0.96 to 95% CI 0.78 to 1.17) [10]. TRAVERSE did not demonstrate increased MACE risk, but it also did not rule out a clinically meaningful increase. The confidence interval upper bound of 1.17 means a 17% increase in MACE remained possible.

Based on TRAVERSE and cumulative post-marketing surveillance, the FDA added a class-wide boxed warning to all testosterone products in June 2023, including Jatenzo [11]. The warning states that testosterone therapy may increase the risk of heart attack and stroke. Dr. Patrizia Cavazzoni, then director of the FDA's Center for Drug Evaluation and Research, stated that "the totality of evidence supports adding this warning to help ensure that prescribers and patients are fully informed about potential cardiovascular risks" [11].

This decision affected Jatenzo specifically because the drug already carried a blood pressure signal that compounded the class-wide concern. A patient on Jatenzo who develops a 5 mmHg systolic BP increase on top of baseline hypertension faces a different risk calculus than the same patient on a transdermal formulation without that hemodynamic effect.

REMS Requirements and Prescribing Restrictions

Jatenzo's REMS (Risk Evaluation and Mitigation Strategy) was required at initial approval and has been modified since [4]. The original REMS included three components: a prescriber certification requirement, a pharmacy enrollment program, and a patient medication guide. Prescribers had to complete training on blood pressure monitoring and hematocrit management before they could prescribe Jatenzo.

The REMS was streamlined in 2021 after post-marketing data showed that prescribers were generally adhering to monitoring requirements without the full certification process [12]. The current REMS retains the medication guide requirement but has simplified prescriber enrollment. Pharmacies dispensing Jatenzo must still be enrolled in the program.

This is notable because most other testosterone formulations do not carry a REMS. Injectable testosterone cypionate, testosterone enanthate, and transdermal gels and patches are prescribed without REMS restrictions. The Jatenzo REMS reflects the FDA's assessment that the oral formulation's blood pressure signal warranted additional safeguards beyond standard labeling.

What Clinicians Should Monitor and When

The Jatenzo prescribing information specifies a monitoring schedule that is more intensive than most testosterone formulations [4]. Blood pressure should be measured at every clinic visit, not just at baseline and follow-up. Hematocrit should be checked at baseline, 3 months, 6 months, and annually. Serum testosterone should be measured at least twice during dose titration to confirm levels remain between 300 and 1 to 100 ng/dL [1].

The American Urological Association's 2018 guideline on testosterone deficiency recommends lipid panel assessment at baseline and 6 to 12 months for all testosterone formulations [13]. For Jatenzo specifically, the label adds that clinicians should evaluate patients for cardiovascular risk factors before initiating therapy and periodically thereafter.

PSA (prostate-specific antigen) monitoring follows the same schedule as other testosterone formulations: baseline, 3 to 6 months, then per age-appropriate screening guidelines. Jatenzo's clinical trials excluded men with PSA >4 ng/mL, so no differential prostate safety data exists for this formulation versus others [1].

Bone mineral density is not routinely monitored for Jatenzo patients unless osteoporosis was the original indication for testosterone therapy. The Endocrine Society recommends DXA scanning at 1 to 2 years for men started on testosterone for osteoporosis-related hypogonadism [6].

Clinicians prescribing Jatenzo should counsel patients that the drug must be taken with a meal containing at least 20 grams of fat, and that blood pressure monitoring may need to be done at home between visits if readings are borderline at baseline.