Repotrectinib

Repotrectinib is an inhibitor of proto-oncogene tyrosine-protein kinase ROS1 (ROS1) and of the tropomyosin receptor tyrosine kinases (TRKs) TRKA, TRKB, and TRKC.

Fusion proteins that include ROS1 domains can drive tumorigenic potential through hyperactivation of downstream signaling pathways leading to unconstrained cell proliferation. Repotrectinib exhibited anti-tumor activity in cultured cells expressing ROS1 fusions and mutations including SDC4-ROS1, SDC4-ROS1^G2032R, CD74-ROS1, CD74-ROS1^G2032R, CD74-ROS1^D2033N, and CD74-ROS1^L2026M.

Repotrectinib exposure-response relationships and the time course of pharmacodynamic responses are not fully characterized.

Cardiac Electrophysiology

Repotrectinib does not cause a mean increase in the QTc interval > 20 milliseconds (ms) at 160 mg QD followed by 160 mg BID, the approved recommended dosage.

The geometric mean (CV%) of repotrectinib steady state peak concentration (C_max,ss) is 713 (32.5%) ng/mL and the area under the time concentration curve (AUC_0-24h,ss) is 7210 (40.1%) ng•h/mL following the approved recommended twice daily dosage in patients with cancer. Repotrectinib C_max and AUC_0-inf increases approximately dose proportional (but less than linear with estimated slopes of 0.78 and 0.70, respectively) over the single dose range of 40 mg to 240 mg (0.25 to 1.5 times the approved recommended dosage). Steady state PK was time-dependent with an autoinduction of CYP3A4. Steady state is achieved within 14 days of daily administration of 160 mg.

Absorption

The geometric mean (CV%) absolute bioavailability of repotrectinib is 45.7% (19.6%). Peak repotrectinib concentration occurred at approximately 2 to 3 hours post a single oral dose of 40 mg to 240 mg (0.25 to 1.5 times the approved recommended dosage) under fasted conditions.

Effect of Food

No clinically significant differences in repotrectinib pharmacokinetics were observed in patients with cancer following administration of a high-fat meal (approximately 800-1000 calories, 50% fat).

Distribution

The geometric mean (CV%) apparent volume of distribution (Vz/F) was 432 L (55.9 %) in patients with cancer following a single 160 mg oral dose of repotrectinib.

Repotrectinib binding to plasma protein was 95.4% in vitro. The blood-to-plasma ratio was 0.56 in vitro.

Elimination

Repotrectinib elimination is time-dependent due to autoinduction of CYP3A4.

The repotrectinib mean terminal half-life is approximately 50.6 h for patients with cancer following a single dose. The steady state repotrectinib terminal half-life is approximately 35.4 h for patients with cancer.

The geometric mean (CV%) apparent oral clearance (CL/F) was 15.9 L/h (45.5%) in patients with cancer following a single 160 mg oral dose of Repotrectinib.

Metabolism

Repotrectinib is primarily metabolized by CYP3A4 followed by secondary glucuronidation.

Excretion

Following a single oral 160 mg dose of radiolabeled repotrectinib, 4.84% (0.56% as unchanged) was recovered in urine and 88.8% (50.6% unchanged) in feces.

Specific Populations

No clinically significant differences in the pharmacokinetics of repotrectinib were observed based on age (18 to 84 years), sex, race/ethnicity (Caucasian 54%, Asian 38%, Black 7%), mild to moderate renal impairment (eGFR 30 to <90 mL/min), or mild hepatic impairment (total bilirubin >1 to 1.5 times ULN or AST > ULN). The effect of moderate (total bilirubin >1.5 to 3 times ULN with any AST) or severe (total bilirubin >3 x ULN with any AST) hepatic impairment, severe renal impairment, kidney failure (eGFR <30 mL/min), or dialysis on repotrectinib pharmacokinetics is unknown or not fully characterized.

Drug Interaction Studies

Clinical Studies

Strong CYP3A and P-gp inhibitors: Repotrectinib AUC_0-inf increased by 5.9-fold and C_max by 1.7-fold following concomitant use with itraconazole (strong CYP3A and P-gp inhibitor).

Strong CYP3A and P-gp inducers: Repotrectinib AUC_0-inf decreased by 92% and C_max by 79% following concomitant use with rifampin (strong CYP3A and P-gp inducer).

CYP3A substrates: Midazolam (CYP3A substrate AUC_0-inf decreased by 69% and C_max by 48% following concomitant use in subjects who were previously administered 160 mg repotrectinib once daily for 14 days followed by 160 mg twice daily for 7 days.

In vitro Studies

CYP Enzymes: Repotrectinib induces CYP3A4, CYP2B6, CYP2C8, CYP2C19, CYP2C9 and inhibits CYP3A4/5 (GI tract). Repotrectinib does not induce CYP1A2.

Other Metabolic Pathways: Repotrectinib inhibits UGT1A1.

Transporter Systems: Repotrectinib inhibits P-gp, BCRP, OATP1B1, and MATE2-K. Repotrectinib is a substrate for P-gp.