Clinical Characteristics and 1-Year Response in Rheumatic Mexican Patients Using JAK Inhibitors

We aim to evaluate the clinical features, first-year treatment response, and frequency of adverse events in Mexican patients receiving Janus kinase inhibitor (JAK-i) using data from the Mexican Adverse Events Registry (BIOBADAMEX). We included all BIOBADAMEX patients from 2022 to 2024 and described the sociodemographic, clinical, treatment characteristics and adverse events of the approved JAK-i in Mexico: tofacitinib, baricitinib, and upadacitinib. We assessed the JAK-i efficacy comparing baseline and the 1-year response mean disease activity scores. A total of 222 patients were included, 39.6% received tofacitinib, 47.3% baricitinib, and 13.1% upadacitinib. The most common diagnosis was rheumatoid arthritis (77%). Sixty-eight percent of patients had comorbidities, 6% had prior history of malignancy, and 57% previously used a biologic. Mean age at JAK-i initiation was 49.6 (±13.9) years with an overall latency period of 9.4 years. DAS28 (Disease Activity Score in 28 joints) reduced from 4.7 (±1.2) at baseline to 2.99 (±1.2) in the first year (p = 0.001), and Bath Ankylosing Spondylitis Disease Activity Index from 4.8 (±3.9) to 2 (±1.5). JAK-i withdrawal was 29%; nonmedical reasons were the main motive. Sixty-five adverse events were reported; all were nonsevere with only 1 case of herpes zoster and no reports of malignancy or thrombosis. Differences in clinical and treatment characteristics between JAK-i were found. Our study showed older age for JAK-i initiation, a lower overall latency period, and lower use of prior biologic disease-modifying antirheumatic drug when compared with existing data in the literature. The main motive for JAK-i withdrawal was nonmedical reasons. Adverse events were nonsevere; interestingly, there was only 1 case of herpes zoster and no reports of malignancy or thrombosis.