Clinical Pharmacology for Rezurock
Mechanism Of Action
Belumosudil is an inhibitor of rho-associated, coiled-coil containing protein kinase (ROCK) which inhibits ROCK2 and ROCK1 with IC50 values of approximately 100 nM and 3 μM, respectively. Belumosudil down-regulated proinflammatory responses via regulation of STAT3/STAT5 phosphorylation and shifting Th17/Treg balance in ex-vivo or in vitro-human T cell assays. Belumosudil also inhibited aberrant pro-fibrotic signaling, in vitro. In vivo, belumosudil demonstrated activity in animal models of chronic GVHD.
Pharmacodynamics
Belumosudil exposure-response relationships and the time course of pharmacodynamic response are not established.
Cardiac Electrophysiology
At 2.4 times the maximum exposure for approved recommended dose, REZUROCK does not prolong the QT interval to any clinically relevant extent.
Pharmacokinetics
The following pharmacokinetic parameters are presented for chronic GVHD patients administered belumosudil 200 mg once daily, unless otherwise specified. The mean (% coefficient of variation, %CV) steady-state AUC and Cmax of belumosudil was 22,700 (48%) h•ng/mL and 2390 (44%) ng/mL, respectively. Belumosudil Cmax and AUC increased in an approximately proportional manner over a dosage range of 200 and 400 mg (1 to 2 times once daily recommended dosage). The accumulation ratio of belumosudil was 1.4.
Absorption
Median Tmax of belumosudil at steady state was 1.26 to 2.53 hours following administration of 200 mg once daily or twice daily in patients. The mean (%CV) bioavailability was 64% (17%) following a single belumosudil dose in healthy subjects.
Effect Of Food
Belumosudil Cmax and AUC increased 2.2 times and 2 times, respectively, following administration of a single belumosudil dose with a high-fat and high-calorie meal (800 to 1,000 calories with approximately 50% of total caloric content of the meal from fat) compared to the fasted state in healthy subjects. Median Tmax was delayed 0.5 hours.
Distribution
The geometric mean volume of distribution after a single dose of belumosudil in healthy subjects was 184 L (geo CV% 67.7%).
Belumosudil binding to human serum albumin and human α1-acid glycoprotein was 99.9% and 98.6%, respectively, in vitro.
Elimination
The mean (%CV) elimination half-life of belumosudil was 19 hours (39%), and clearance was 9.83 L/hours (46%) in patients.
Metabolism
Belumosudil is primarily metabolized by CYP3A4 and to a lesser extent by CYP2C8, CYP2D6, and UGT1A9, in vitro.
Excretion
Following a single oral dose of radiolabeled belumosudil in healthy subjects, 85% of radioactivity was recovered in feces (30% as unchanged) and less than 5% in urine.
Specific Populations
No clinically significant differences in belumosudil pharmacokinetics were observed with regard to age (18 to 77 years), sex, weight (38.6 to 143 kg), or mild to moderate renal impairment (eGFR ≥60 and <90 mL/min/1.72m² to eGFR ≥30 and <60 mL/min/1.72m²). The effect of severe renal impairment on the pharmacokinetics of belumosudil has not been studied.
Patients With Hepatic Impairment
Following a single 200 mg dose of belumosudil, changes in belumosudil exposure in subjects with varying degrees of hepatic impairment based on Child-Pugh score without liver GVHD relative to subjects with normal hepatic function is shown in Table 4.
Table 4: Effect of Varying Degrees of Hepatic Impairment on Belumosudil Exposure
| Hepatic Impairment Category |
Changes in Belumosudil Exposure in Subjects with Hepatic Impairment Compared to Subjects with Normal Hepatic Function |
| Total (Free + Bound) Concentrations |
Free Concentrations |
| Cmax |
AUC |
Cmax |
AUC |
| Mild (Child-Pugh A) |
1.2-fold increase |
1.4-fold increase |
14% decrease |
19% decrease |
| Moderate (Child-Pugh B) |
6% decrease |
1.5-fold increase |
12% decrease |
1.4-fold increase |
| Severe (Child-Pugh C) |
1.3-fold increase |
4.2-fold increase |
5.4-fold increase |
16-fold increase |
Drug Interaction Studies
Clinical studies and model-informed approaches
Effects Of Other Drugs On Belumosudil
Strong Cytochrome P450 (CYP) 3A Inhibitors: There was no clinically meaningful effect on belumosudil exposure when coadministered with itraconazole in healthy subjects.
Strong CYP3A Inducers: Coadministration of rifampin decreased belumosudil Cmax by 59% and AUC by 72% in healthy subjects.
Moderate CYP3A Inducers: Coadministration of efavirenz is predicted to decrease belumosudil Cmax by 19% and AUC by 35% in healthy subjects.
Proton Pump Inhibitors: Coadministration of rabeprazole decreased belumosudil Cmax by 87% and AUC by 80%, and omeprazole decreased belumosudil Cmax by 68% and AUC by 47% in healthy subjects.
Effects Of Belumosudil On Other Drugs
CYP3A Substrates: Coadministration of belumosudil is predicted to increase midazolam (a sensitive CYP3A substrate) Cmax and AUC approximately 1.3- and 1.5-fold, respectively.
CYP2C9 Substrates: Coadministration of belumosudil is not expected to have clinically meaningful effect on the exposure of CYP2C9 substrates (such as warfarin).
CYP2C8 Substrates: Coadministration of belumosudil is not expected to have clinically meaningful effect on the exposure of CYP2C8 substrates that are not an OATP1B1 substrate.
UGT1A1 Substrates: Coadministration of belumosudil decreased raltegravir glucuronide (metabolite formed via the UGT1A1 pathway) Cmax by 42% and AUC by 40%.
Transporter Systems
OATP1B1/BCRP Substrates: Coadministration of belumosudil increased rosuvastatin (OATP1B1 and BCRP substrate) Cmax and AUC by 3.6- and 4.6-fold, respectively.
P-glycoprotein (P-gp) Substrates: Coadministration of belumosudil increased dabigatran (P-gp substrate) Cmax and AUC by 2-fold.
In Vitro studies
Transporter Systems
Belumosudil is a substrate of P-gp. Belumosudil inhibits BCRP, P-gp, and OATP1B1 at clinically relevant concentrations.
Enzymes Systems
Belumosudil is an inhibitor of CYP1A2, CYP2C19, CYP2D6, UGT1A1 and UGT1A9.
Clinical Studies
Chronic Graft Versus Host Disease
Study KD025-213 (NCT03640481) was a randomized, open-label, multicenter study of REZUROCK for treatment of patients with chronic GVHD who had received 2 to 5 prior lines of systemic therapy and required additional treatment. Patients were excluded from the studies if platelets were <50 × 109/L; absolute neutrophil count <1.5 × 109/L; AST or ALT >3 × ULN; total bilirubin >1.5 × ULN; QTc(F) >480 ms; eGFR <30 mL/min/1.73 m²; or FEV1 ≤39%. There were 66 patients treated with REZUROCK 200 mg taken orally once daily. Concomitant treatment with supportive care therapies for chronic GVHD was permitted. Concomitant treatment with GVHD prophylaxis and standard care systemic chronic GVHD therapies was permitted as long as the subject has been on a stable dose for at least 2 weeks prior to study. Initiation of new systemic chronic GVHD therapy while on study was not permitted.
Demographics and baseline characteristics are summarized in Table 5.
Table 5: Demographics and Baseline Characteristics of Patients with Chronic GVHD
|
REZUROCK 200 mg once daily
(N=65) |
| Age, Median, Years (minimum, maximum) |
53 (21, 77) |
| Age ≥65 Years, n (%) |
17 (26) |
| Male, n (%) |
42 (65) |
| Race, n (%) |
| White |
54 (83) |
| Black |
6(9) |
| Other or Not Reported |
5 (8) |
| Median (range) time (months) from Chronic GVHD Diagnosis |
25.3 (1.9, 162.4) |
| ≥4 Organs Involved, n (%) |
31 (48) |
| Median (range) Number of Prior Lines of Therapy |
3 (2, 6) |
| Number of Prior Lines of Therapy, n (%) |
| 2 |
23 (35) |
| 3 |
12(19) |
| 4 |
15 (23) |
| ≥5 |
15 (23) |
| Prior chronic GVHD treatment with ibrutinib, n (%) |
21 (32) |
| Prior chronic GVHD treatment with ruxolitinib, n (%) |
20 (31) |
| Refractory to Last Therapy, n (%*) |
43/55 (78) |
| Severe chronic GVHD, n (%) |
46 (71) |
| Median (range) Global Severity Rating |
7 (2, 9) |
| Median (range) Lee Symptom Scale Score at baseline |
27 (7, 56) |
| Median (range) Corticosteroid dose at baseline (PE/kg)† |
0.19 (0.03, 0.95) |
* Denominator excludes patients with unknown status
† Prednisone equivalents/kilogram |
The efficacy of REZUROCK was based on overall response rate (ORR) through Cycle 7 Day 1 where overall response included complete response or partial response according to the 2014 NIH Response Criteria. The ORR results are presented in Table 6. The ORR was 75% (95% CI: 63, 85). The median duration of response, calculated from first response to progression, death, or new systemic therapies for chronic GVHD, was 1.9 months (95% CI: 1.2, 2.9). The median time to first response was 1.8 months (95% CI: 1.0, 1.9). In patients who achieved response, no death or new systemic therapy initiation occurred in 62% (95% CI: 46, 74) of patients for at least 12 months since response.
Table 6: Overall Response Rate through Cycle 7 Day 1 for Patients with Chronic GVHD in Study KD025-213
|
REZUROCK 200 mg once daily
(N=65) |
| Overall Response Rate (ORR) |
49 (75%) |
| 95% Confidence Interval* |
(63%, 85%) |
| Complete Response |
4 (6%) |
| Partial Response |
45 (69%) |
| * Estimated using Clopper-Pearson method |
ORR results were supported by exploratory analyses of patient-reported symptom bother which showed at least a 7-point decrease in the Lee Symptom Scale summary score through Cycle 7 Day 1 in 52% (95% CI: 40, 65) of patients.