AYVAKIT Film-coated tablet Ref.[9993] Active ingredients:

Exposure-Response Relationships

Based on the data from NAVIGATOR, exposure-response relationships for any Grade 3 or 4 adverse reaction were observed at higher exposures with a faster time to onset for adverse reactions with increasing avapritinib exposure.

Cardiac Electrophysiology

The effect of AYVAKIT on the QTc interval was evaluated in an open-label, single-arm study in 27 patients administered dose of 300 mg or 400 mg (1.3 times the approved recommended dose) once daily. No large mean increase in QTc (i.e. >20 ms) was detected at the mean steady state maximum concentration (C_max) of 899 ng/mL.

Avapritinib C_max and AUC increased proportionally over the dose range of 30 mg to 400 mg once daily (0.1 to 1.33 times the recommended dose).

At the recommended dosage of 300 mg once daily, the mean (CV%) steady state C_max of avapritinib was 813 ng/mL (52%) and the mean steady state area under the concentration-time curve (AUC_0-24h) was 15400 h∙ng/mL (48%). Steady state concentration of avapritinib was reached by day 15 following daily dosing and the mean accumulation ratio was 3.1 to 4.6 after repeated dosing.

Absorption

The median time to peak concentration (T_max) ranged from 2.0 to 4.1 hours following single doses of avapritinib 30 mg to 400 mg (0.1 to 1.33 times the approved recommended dose).

Effect of Food

The C_max of avapritinib was increased by 59% and the AUC_0-INF was increased by 29% when AYVAKIT was taken with a high-calorie, high-fat meal (approximately 909 calories, 58 grams carbohydrate, 56 grams fat and 43 grams protein) compared to those in the fasted state.

Distribution

The mean apparent volume of distribution of avapritinib is 1200 L (43%). In vitro protein binding of avapritinib is 98.8% and is independent of concentration. The blood-to-plasma ratio is 0.95.

Elimination

The mean plasma elimination half-life of avapritinib was 32 hours to 57 hours following single doses of avapritinib 30 mg to 400 mg (0.1 to 1.33 times the approved recommended dose). The steady state mean apparent oral clearance of avapritinib is 19.5 L/h (48%).

Metabolism

Avapritinib is primarily metabolized by CYP3A4 and to a lesser extent by CYP2C9 in vitro. Following a single oral dose of approximately 310 mg of radiolabeled avapritinib to healthy subjects, unchanged avapritinib (49%) and its metabolites M690 (hydroxy glucuronide; 35%) and M499 (oxidative deamination; 14%) were the major circulating compounds. Following oral administration of AYVAKIT 300 mg once daily in patients, the steady state AUC of M499 is approximately 80% of the AUC of avapritinib. M499 is not likely to contribute to efficacy at the recommended dose of avapritinib.

Excretion

Following a single oral dose of approximately 310 mg of radiolabeled avapritinib to healthy subjects, 70% of the radioactive dose was recovered in feces (11% unchanged) and 18% in urine (0.23% unchanged).

Specific Populations

No clinically significant differences in the pharmacokinetics of avapritinib were observed based on age (18 to 90 years), sex, race (White, Black, or Asian), body weight (39.5 to 156.3 kg), mild to moderate (CLcr 30 to 89 mL/min estimated by Cockcroft-Gault) renal impairment, or mild (total bilirubin ≤ ULN and AST > ULN or total bilirubin >1 to 1.5 times ULN and any AST) to moderate (total bilirubin >1.5 to 3 times ULN and any AST) hepatic impairment. The effect of severe renal impairment (CLcr 15 to 29 mL/min), end-stage renal disease (CLcr < 15 mL/min), or severe hepatic impairment (total bilirubin >3 times ULN and any AST) on the pharmacokinetics of avapritinib is unknown.

Drug Interaction Studies

Clinical Studies and Model-Informed Approaches

Effect of Strong and Moderate CYP3A Inhibitors on Avapritinib: Coadministration of AYVAKIT 300 mg once daily with itraconazole 200 mg once daily (a strong CYP3A inhibitor) is predicted to increase avapritinib AUC by 600% at steady state.

Coadministration of AYVAKIT 300 mg once daily with fluconazole 200 mg once daily (a moderate CYP3A inhibitor) is predicted to increase avapritinib AUC by 210% at steady state [see Drug Interactions (7.1)].

Effect of Strong and Moderate CYP3A Inducers on Avapritinib: Coadministration of AYVAKIT 400 mg as a single dose with rifampin 600 mg once daily (a strong CYP3A inducer) decreased avapritinib C_max by 74% and AUC_0-INF by 92%.

Coadministration of AYVAKIT 300 mg once daily with efavirenz 600 mg once daily (a moderate CYP3A inducer) is predicted to decrease avapritinib C_max by 55% and AUC by 62% at steady-state [see Drug Interactions (7.1)].

Effect of Acid-Reducing Agents on Avapritinib: No clinically significant differences in the pharmacokinetics of avapritinib were identified when coadministered with gastric acid reducing agents in patients with GIST.

In Vitro Studies

Cytochrome P450 (CYP) Enzymes: In vitro studies indicate that avapritinib is a time-dependent inhibitor as well as an inducer of CYP3A at clinically relevant concentrations.

Avapritinib is an inhibitor of CYP2C9 at clinically relevant concentrations. Avapritinib is not an inhibitor of CYP1A2, CYP2B6, CYP2C8, CYP2C19, or CYP2D6 at clinically relevant concentrations.

Avapritinib is not an inducer of CYP1A2 or CYP2B6. Avapritinib is a substrate of CYP3A.

M499 is an inhibitor of CYP3A, CYP2C8, or CYP2C9 at clinically relevant concentrations. M499 is not an inhibitor of CYP1A2, CYP2B6, CYP2C19, or CYP2D6 at clinically relevant concentrations.

Transporter Systems: Avapritinib is an inhibitor of P-glycoprotein (P-gp), intestinal BCRP, MATE1, MATE2-K, and BSEP, but not an inhibitor of OATP1B1, OATP1B3, OAT1, OAT3, OCT1, or OCT2. Avapritinib is not a substrate of P-gp or BCRP. The effect of M499 on transporter systems is unknown.

Carcinogenicity studies with avapritinib have not been conducted. Avapritinib was not mutagenic in vitro in the bacterial reverse mutation assay (Ames test). Avapritinib was clastogenic in the in vitro chromosome aberration test in human peripheral blood lymphocytes but not clastogenic in the in vivo rat bone marrow micronucleus test.

Avapritinib may impair fertility in humans. Administration of avapritinib to female rats for up to 3 months resulted in cystic degeneration of corpora lutea at doses greater than or equal to 5 mg/kg/day (approximately 1.3 times the human exposure based on AUC at the 300 mg dose). Administration of avapritinib to male dogs for up to 3 months resulted in hypo-spermatogenesis at doses greater than or equal to 7.5 mg/kg/day (approximately 0.4 times the human exposure based on AUC at the 300 mg dose).

In repeat dose toxicology studies, administration of avapritinib to rats and dogs for up to 3 months resulted in tremors at doses greater than or equal to 30 mg/kg/day (approximately 1.5 times the human exposure based on AUC at the 300 mg dose). Hemorrhage in the brain and spinal cord and choroid plexus edema in the brain occurred in dogs at doses greater than or equal to 7.5 mg/kg/day (approximately 0.4 times the human exposure based on AUC at the 300 mg dose).

An in vitro phototoxicity study in 3T3 mouse fibroblasts and an in vivo phototoxicity study in pigmented rats demonstrated that avapritinib has a slight potential for phototoxicity.

14.1 Gastrointestinal Stromal Tumors

The efficacy of AYVAKIT was demonstrated in NAVIGATOR (NCT02508532), a multi-center, single-arm, open-label clinical trial. Eligible patients were required to have a confirmed diagnosis of GIST and an ECOG performance status (PS) of 0 to 2. Patients received AYVAKIT 300 mg or 400 mg orally once daily until disease progression or unacceptable toxicity. The trial initially enrolled patients at a starting dose of 400 mg, which was later reduced to the recommended dose of 300 mg due to toxicity. As there was no apparent difference in overall response rate (ORR) between patients who received 300 mg daily compared to those who received 400 mg daily, these patients were pooled for the efficacy evaluation. The major efficacy outcome measure was ORR based on disease assessment by independent radiological review using modified RECIST v1.1 criteria, in which lymph nodes and bone lesions were not target lesions and progressively growing new tumor nodules within a pre-existing tumor mass was progression. An additional efficacy outcome measure was duration of response (DOR).

Patients with GIST Harboring a PDGFRA Exon 18 Mutation

Patients with unresectable or metastatic GIST harboring a PDGFRA exon 18 mutation were identified by local or central assessment using a PCR- or NGS-based assay. The assessment of efficacy was based on a total of 43 patients, including 38 patients with PDGFRA D842V mutations. The median duration of follow up for patients with PDGFRA exon 18 mutations was 10.6 months (range: 0.3 to 24.9 months).

The study population characteristics were median age of 64 years (range: 29 to 90 years), 67% were male, 67% were White, 93% had an ECOG PS of 0-1, 98% had metastatic disease, 53% had largest target lesion >5 cm, and 86% had prior surgical resection. The median number of prior kinase inhibitors was 1 (range: 0 to 5).

Efficacy results in patients with GIST harboring PDGFRA exon 18 mutations including the subgroup of patients with PDGFRA D842V mutations enrolled in NAVIGATOR are summarized in Table 5.

Table 5. Efficacy Results for Patients with GIST Harboring PDGFRA exon 18 mutations in NAVIGATOR

Abbreviations: CI=confidence interval; NR=not reached; NE=not estimable
⁺ Denotes ongoing response
^* Exon 18 mutations other than D84 2V included in this population are: deletion of D84 2_H84 5 (n=3); D84 2Y (n=1); and deletion of D84 2_H84 5 with insertion of V (n=1).
^† 11 patients with an ongoing response were followed <6 months from onset of response.