A Phase 1 Pharmacokinetic Drug Interaction Study of Belumosudil Coadministered With CYP3A4 Inhibitors and Inducers and Proton Pump Inhibitors

Two-Part Phase 1 Study to Evaluate the Taste Profile of Novel Belumosudil Oral Suspensions and Assess the Relative Bioavailability and Food Effect of the Selected Belumosudil Oral Suspension Compared With Oral Tablet Reference in Healthy Male Participants

Belumosudil is a selective rho-associated coiled-coil-containing protein kinase 2 inhibitor in clinical use for the treatment of chronic graft-versus-host disease. The current tablet formulation may be inappropriate for children or adults with dysphagia and/or upper gastrointestinal manifestations of chronic graft-versus-host disease. This study (NCT04735822) assessed the taste and palatability of oral suspensions of belumosudil, evaluated the relative bioavailability of an oral suspension versus the tablet formulation, and characterized the effect of food on the pharmacokinetics of an oral suspension. Addition of sweetener and/or flavor vehicle improved the taste. Relative bioavailability of 200-mg doses of the oral suspension and tablet in the fed state was similar for belumosudil and its metabolites (KD025m1 and KD025m2), but absorption was faster with the oral suspension (median time to maximum concentration: 2 vs 3 hours). Administration of the oral suspension with food increased exposure compared with fasted administration, with maximum observed concentration being increased by 16% and area under the concentration-time curve from time 0 to the last measurable concentration (AUC0-last) by 19%. Safety and tolerability were consistent with the known safety profile of belumosudil. These results may support administration of a 200-mg belumosudil oral suspension with or without food.

Belumosudil Impacts Immunosuppression Pharmacokinetics in Patients with Chronic Graft-versus-Host Disease

Belumosudil (BEL) is a novel Rho-associated coiled-coil containing protein kinase 2 (ROCK2) inhibitor approved for the treatment of chronic graft-versus-host disease (cGVHD) in patients who have failed 2 or more prior lines of systemic therapy. Although the pharmacokinetic effects of BEL on other immunosuppressive (IS) agents have not been clinically evaluated, in vitro data indicate that BEL may have possible interactions with drugs with a narrow therapeutic index used to treat cGVHD, such as tacrolimus, sirolimus, and cyclosporine, through cytochrome P450 (CYP3A) and p-glycoprotein interactions. Further evaluation of these potential interactions is warranted to optimize the safety and effectiveness of these medications when combined with BEL. In this study, we investigated the potential effects of BEL on sirolimus and tacrolimus levels when used concurrently by assessing changes in IS levels after the addition of BEL. This retrospective single-center study of patients who started BEL while on tacrolimus and/or sirolimus between February 1, 2019, to February 1, 2023, included patients who had IS levels measured at baseline prior to starting BEL and at least 1 subsequent IS measurement to assess changes over time. The primary endpoint was the concentration-dose (C/D) ratio analyzed before and after the addition of BEL. Secondary endpoints included the incidence of IS levels outside of the therapeutic range (subtherapeutic or supratherapeutic) and mean dosage changes over time. Thirty-seven patients met our eligibility criteria and were included in this analysis. Patients taking sirolimus (n = 30) or tacrolimus (n = 16) concurrently with BEL had a statistically significant increase in the C/D ratio (sirolimus recipients, 160% [P < .001]; tacrolimus recipients, 113% [P = .013]) between the pre-BEL and final post-BEL assessments. The C/D ratios for both tacrolimus and sirolimus recipients continued to increase at several time points after initiation of BEL, indicating that multiple drug dosage adjustments may be required. After BEL initiation, 19% of tacrolimus levels and 57% of sirolimus levels were supratherapeutic. Despite dosage adjustments, 27% of tacrolimus levels were supratherapeutic at both the second and third assessments after starting BEL, and 28% and 30% of sirolimus levels were supratherapeutic at these 2 time points, respectively. All 12 of the patients who discontinued BEL during the study period (100%) showed a return to their baseline C/D ratio, confirming that the C/D ratio change can be attributed to BEL. The impact of BEL on IS levels is clinically significant, warranting dosage adjustments of concurrent medications. A significant number of patients taking sirolimus with BEL had levels >15 ng/mL during the study period, indicating a potential risk for toxicity if this interaction is unmonitored. We recommend empiric dose reductions of 25% for tacrolimus and 25% to 50% for sirolimus when adding BEL, as well as close monitoring of IS levels during the initial weeks of BEL therapy. Future studies are warranted to better describe the impact of BEL on patients taking CYP3A inhibitors.

A Phase 1 Thorough QT/QTc Study of Therapeutic and Supratherapeutic Doses of Belumosudil in Healthy Subjects

Belumosudil is a selective Rho-associated, coiled-coil-containing protein kinase-2 inhibitor. In this crossover design thorough QT/QTc study, single therapeutic (200 mg) and supratherapeutic (1000 mg) oral doses of belumosudil, moxifloxacin (positive control), and placebo were administered to 34 subjects. Twelve-lead electrocardiograms and serial pharmacokinetic sampling were acquired. The effect of belumosudil on the placebo-corrected, change-from-baseline QTcF was small, and an effect exceeding 10 ms could be excluded across all time points with both doses. Using concentration-QTc analysis, an effect on ΔΔQTcF >10 ms can be excluded up to belumosudil concentrations of ≈12 080 ng/mL, more than 2-fold above mean C_max after the supratherapeutic dose. There was no clinically relevant effect on heart rate or cardiac conduction (ie, the PR and QRS intervals) for belumosudil. No differences in safety were noted between belumosudil and placebo treatment. Assay sensitivity was demonstrated by moxifloxacin's effect on the QTc interval. In conclusion, belumosudil at therapeutic and supratherapeutic doses did not have a clinically meaningful effect on electrocardiogram parameters.