Hypomagnesemia in lymphoma patients exposed to romidepsin

Background: Romidepsin (R) is indicated for cutaneous T-cell lymphoma (CTCL) and peripheral T-cell lymphoma. Hypomagnesemia (HM) is common in these patients and is also listed in the Full Prescribing Information (FPI) for R. Moreover, since cardiac arrhythmias are associated with HM, patients exposed to R may be at higher risk. This study assessed whether HM was causally related to R exposure and to what extent magnesium (M) supplementation was undertaken in those with HM. Methods: We searched a large, U.S. patient data repository to detect all patients (aged 20-94 years) exposed to R (10/2010-01/2017). For these patients, serum M, as well as M supplementation data, was collected. Baseline M was assessed at initial R exposure, and HM was defined as either, a decline in M to <1.8 mg/dL after R exposure or, in those with baseline M <1.8 mg/dL, a decline in M by ≥0.1 mg/dL after R exposure. For each patient with HM after R exposure, the validated Naranjo Adverse Drug Reaction Probability Scale (NADRPS) was used to determine the probability that HM was caused by R. Results: Of 51 R-exposed CTCL (or other lymphoma) patients, 25 (49.0%) had HM. Of these 25, NADRPS scores yielded: 1 doubtful, 16 possible, 8 probable and 0 definite. Additionally, 24 of 25 patients with HM had documentation for presence or absence of M supplementation: 9 (37.5%) had supplementation with M agents considered to be bioavailable, 12 (50%) received M agents considered to have low bioavailability, and 3 (12.5%) had no M supplementation. Conclusions: In this study population, 25 of 51 (49.0%) patients had HM after R exposure, which appears to nearly double the percentage of patients described in the FPI. Moreover, 8 of 25 (32%) patients with HM had causality attributed to R exposure. In addition, 15 of 24 (63%) patients with HM received M supplementation with agents considered to have low bioavailability or received no M supplementation. These findings support the need for ongoing monitoring of R-exposed patients with low M, as well as the importance of repleting M with agents considered to be adequately bioavailable. Also, given that HM appears to be more frequent in this study population compared to pre-marketing data in the FPI, further studies are warranted.