Effects of filgotinib on semen parameters and sex hormones in male patients with inflammatory diseases: results from the phase 2, randomised, double-blind, placebo-controlled MANTA and MANTA-RAy studies

Objectives The phase 2 MANTA and MANTA-RAy studies aimed to determine if the oral Janus kinase 1 preferential inhibitor filgotinib affects semen parameters and sex hormones in men with inflammatory diseases. Methods MANTA (NCT03201445) and MANTA-RAy (NCT03926195) included men (21-65 years) with active inflammatory bowel disease (IBD) and rheumatic diseases (rheumatoid arthritis, spondyloarthritis or psoriatic arthritis), respectively. Eligible participants had semen parameters in the normal range per the WHO definition. In each study, participants were randomised 1:1 to receive once-daily, double-blind filgotinib 200 mg or placebo for 13 weeks for pooled analysis of the primary endpoint (proportion of participants with a >= 50% decrease from baseline in sperm concentration at week 13). Participants who met the primary endpoint were monitored over an additional 52 weeks for 'reversibility'. Secondary endpoints included change from baseline to week 13 in: sperm concentration, total motility, normal morphology, total count and ejaculate volume. Sex hormones (luteinising hormone, follicle stimulating hormone, inhibin B and total testosterone) and reversibility were exploratory endpoints. Results Across both studies, 631 patients were screened, and 248 were randomised to filgotinib 200 mg or placebo. Baseline demographics and characteristics were similar within indications between treatment groups. Numerically similar proportions of filgotinib-treated versus placebo-treated patients met the primary endpoint (8/120 (6.7%) vs 10/120 (8.3%)), Delta-1.7% (95% CI -9.3% to 5.8%)). There were no clinically relevant changes from baseline to week 13 in semen parameters or sex hormones, or patterns of reversibility between treatment groups. Filgotinib was well tolerated, with no new safety events. Conclusions Results suggest that once daily filgotinib 200 mg for 13 weeks has no measurable impact on semen parameters or sex hormones in men with active IBD or inflammatory rheumatic diseases.