Effects of CYP3A Inhibition, CYP3A Induction, and Gastric Acid Reduction on the Pharmacokinetics of Ripretinib, a Switch Control KIT Tyrosine Kinase Inhibitor

Effect of Verapamil, a P-glycoprotein-1 and Cytochrome P450 3A4 Inhibitor, on Pharmacokinetics and Metabolic Stability of Ripretinib: A Drug-Drug Interaction Study in Rats

BACKGROUND AND OBJECTIVES

Ripretinib was developed to target a whole range of KIT proto-oncogene mutations and platelet-derived growth factor receptor A (PDGFR-A) kinases found in certain cancers and myeloproliferative neoplasms, particularly gastrointestinal stromal tumours (GISTs). This study investigated the effect of verapamil, a potential inhibitor of P-glycoprotein-1 (P-gp1) and cytochrome P450 3A4 (CYP3A4), on the pharmacokinetics of ripretinib in rats when administered orally together. This study also assessed the metabolic stability and in vitro cellular absorption of ripretinib in the presence of verapamil.

METHODS

A novel sensitive time-saving liquid chromatography tandem mass spectometry (LC-MS/MS) technique for determining ripretinib in rat plasma was developed and validated. A Zorbax SB C18 column was used for the separation and analysis of ripretinib with a mobile phase consisting of 50:50 (%v/v) acetonitrile and 10 mM ammonium formate buffer at a flow rate of 0.4 mL/min. Imatinib was used as an internal standard (IS) in the method. The pharmacokinetic characteristics of ripretinib were evaluated in Wistar rats by successfully administering an oral dosage of 5 mg/kg body weight of ripretinib in the presence of verapamil (10 mg/kg body weight). Subsequently, rat liver microsomes were used to assess the effect of verapamil on ripretinib metabolic stability, and absorption was tested using a Caco-2 cell transwell model.

RESULTS

Ripretinib and IS were identified using multiple reaction monitoring (MRM) modes by mass spectrometry and showed ion transitions of 510.09→94.06 m/z and 494.26→ 394.16 m/z, respectively. The high-performance liquid chromatography (HPLC) method successfully eluted ripretinib and IS at retention times of 0.91 and 0.68 min, respectively, and the method was validated for all parameters and met the criteria for acceptance. Co-administration of verapamil increased the maximum concentration (Cmax) of ripretinib from 437 ± 84 ng/mL to 492 ± 50 ng/mL (12%), and the area under the concentration-time curve from 0 to the last sampling time t (AUC0-t) increased by approximately 40.6%. Verapamil significantly reduced the basolateral-to-apical transfer of ripretinib through Caco-2 cells. Findings also showed that verapamil increased the metabolic stability of ripretinib.

CONCLUSION

The study results indicate that the co-administration of ripretinib with CYP3A4 and/or P-gp1 inhibitors is associated with significant drug-drug interactions that affect the pharmacokinetics of ripretinib. Further research in human subjects is suggested to confirm dosage adjustment and therapeutic drug monitoring of ripretinib when administered along with P-gp1/CYP3A4 inhibitors ensuring patient safety and optimizing the therapeutic benefits of ripretinib.

Evaluation of Systemic Treatment Options for Gastrointestinal Stromal Tumours

Gastrointestinal stromal tumours (GIST) are the most common mesenchymal tumours of the gastrointestinal tract. Surgical treatment is recommended for the majority of localised GIST, while systemic treatment is the cornerstone of management for metastatic or unresectable disease. While a three-year regimen of imatinib is the standard of care in the adjuvant setting, there is no precise recommendation for the duration of neoadjuvant treatment, where imatinib is usually given between 4 and 12 months. Continuous treatment with imatinib at a dose of 400 mg once per day is recommended for most patients with unresectable or metastatic GIST in the first line. An exception is represented by patients with tumours harbouring the imatinib-insensitive PDGFRA D842V mutation who would be better treated with avapritinib. Targeted therapies are also recommended in the presence of NTRK rearrangements and BRAF mutations, although limited data are available. While an increase in the dose of imatinib to 800 mg is an option for the second line, sunitinib is usually considered the standard of care. Similar outcomes were reported for ripretinib in patients with tumours harbouring KIT exon 11 mutation, with significantly fewer side effects. Regorafenib and ripretinib are the standards of care in the third and fourth lines, respectively. The recent development of various systemic treatment options allows for a more personalised approach based on the molecular profile of the GIST, patient characteristics, and the profile of medications' adverse events. A multidisciplinary approach is paramount since combining systemic treatment with locoregional treatment options and supportive care is vital for long-term survival.

Evaluating the impact of co-administered drug and disease on ripretinib exposure: A physiologically-based pharmacokinetic modeling approach

Ripretinib, as an oral kinase inhibitor, has been approved to treat advanced gastrointestinal stromal tumors (GIST) and is often used in combination with other drugs to slow disease progression, thus potential drug-drug Interactions (DDIs) and drug-disease interactions (DDZIs) have received much attention. To guide clinical rational drug use, this study assessed the effect of co-administered drugs and diseases on ripretinib exposure. Simcyp® Simulator was used to develop the physiologically-based pharmacokinetic (PBPK) model of ripretinib, which was validated and refined with clinical data. We then examined the impact of several CYP3A4 inhibitors and inducers as well as different diseases on ripretinib exposure using the validated model. In the DDI simulation, moderate CYP3A4 inhibitors and inducers changed the exposure of ripretinib by 1.25-2 fold. In hepatic impairment (HI), the simulation showed that ripretinib's AUC increased by 32%, 100%, and 152% for Child-Pugh A, B, and C classification while C_max increased by 2%, 10%, and 15%, respectively. In renal impairment (RI), the model-simulated AUC in moderate and severe RIs increased by 27% and 20%. In conclusion, PBPK models demonstrated quantitative prediction of ripretinib's pharmacokinetic changes under varying conditions that might be useful for its rational use.