Ripretinib intrapatient dose escalation after disease progression provides clinically meaningful outcomes in advanced gastrointestinal stromal tumour

Liquid chromatography-tandem mass spectrometry for the quantification of ripretinib and its metabolites DP-5439 in human plasma

Background

Ripretinib, a broad-spectrum tyrosine kinase inhibitor, has been approved for the treatment of advanced gastrointestinal stromal tumors in adult patients. Clinical studies have shown that higher in vivo exposure of ripretinib correlates with improved efficacy, highlighting the potential clinical significance of therapeutic drug monitoring. In this study, a simple and stable liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was attempted to be established and validated for pharmacokinetic studies of ripretinib and its metabolite DP-5439 and therapeutic drug monitoring in human plasma.

Method

Ripretinib and DP-5439 were separated by chromatography using a Thermofisher Hypersil GOLDTM C18 HPLC column. The mobile phase for gradient elution is composed of 0.1% formic acid in water and acetonitrile. Multiple reaction monitoring was implemented along with electrospray ionization positive mode for detection. The ion pairs of ripretinib, DP-5439 and internal standard D8-ripretinib were m/z 510.1→m/z 417, m/z 496.11→m/z 402.9 and m/z 518.15→m/z 420, respectively. Plasma samples from ripretinib-treated patients of our hospital were collected for pharmacokinetic analysis.

Results

Ripretinib and DP-5439 demonstrated a strong linear relationship over 10-5,000 μg/L (R 2 > 0.99). Accuracy, precision, specificity, recoveries, matrix effect, stability, and dilution effect were all validated and found to meet the required criteria. Following validation, the method was utilized to determine plasma samples from patients treated with ripretinib. The median steady-state trough concentrations (Cmin, range) were 398.50 (66.98 ∼ 1,458.91) μg/L for ripretinib and 654.74 (30.71 ∼ 1,522.48) μg/L for DP-5439, with a total median concentration of 1,129.46 (140.95 ∼ 2,981.39) μg/L in patients receiving ripretinib at 150 mg once daily. Meanwhile, using the established methods, the study conducted pharmacokinetics studies on four patients with ripretinib and DP-5439.

Conclusion

This study developed and validated a robust LC-MS/MS method for determining ripretinib and its metabolite DP-5439 in human plasma. Furthermore, the practicality of this method in clinical sample analysis was demonstrated. This approach can serve as an effective tool for the pharmacokinetics analysis and therapeutic drug monitoring in patients treated with ripretinib.

Ripretinib for the treatment of advanced, imatinib-resistant gastrointestinal stromal tumors

Discovery of constitutive activation of KIT/PDGFRA tyrosine kinases in gastrointestinal stromal tumors (GISTs) leads to the development of the targeted drug imatinib. However, the inevitable development of imatinib resistance remains a major issue. Ripretinib is a novel targeted drug that inhibits the activities of a broad spectrum of drug-resistant KIT/PDGFRA mutants. It was approved in 2020 and is currently recommended by major international guidelines as the fourth-line and beyond therapy for advanced GISTs. Emerging evidence shows that ripretinib is superior to sunitinib as a second-line treatment for KIT exon 11-mutated GISTs due to its activity against highly heterogeneous frequently occurring secondary mutations. This review summarizes current data on the use of ripretinib to treat advanced imatinib-resistant GISTs. We also propose future research directions to improve the targeted GIST treatment.

Effect and safety of ripretinib in the treatment of advanced gastrointestinal stromal tumor: A systematic review and meta-analysis

BACKGROUND

Imatinib (IMA) has received approval as the primary treatment for gastrointestinal stromal tumors (GIST). Nonetheless, approximately half of the patients with advanced GIST show disease advancement following IMA treatment. Presently, the efficacy of secondary and tertiary medications in addressing various GIST secondary mutations is somewhat restricted. Consequently, there is a significant medical demand for the creation of kinase inhibitors that extensively block secondary drug-resistant mutations in advanced GIST. Ripretinib (RPT) is a new, switch-control tyrosine kinase inhibitors that can suppress different mutations of KIT and PDGFRA via a dual mechanism of action.

AIM

To investigate the literature on RPT to assess an effective, safe, and successful treatment strategy against advanced GIST.

METHODS

The present systematic review and meta-analysis was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed, Embase, Cochrane, Web of Science and ClinicalTrials.gov databases were screened from January 1, 2003 to May 1, 2024.

RESULTS

A total of 4 studies were included, with a total of 507 patients enrolled. The objective response rate (ORR) of the RPT-treated advanced GIST was 17% (95%CI: 0.11-0.27), while the disease control rate (DCR) was 66% (95%CI: 0.59-0.73). The overall occurrence of adverse events with varying degrees was 97% (95%CI: 0.93-1), whereas that of grade ≥ 3 adverse reactions was 42% (95%CI: 0.28-0.63). The sensitivity analysis revealed that omitting some studies did not yield statistically notable variances in the aggregate data regarding the ORR, DCR, and the occurrence of adverse events of grade 3 or higher. The publication bias was absent because no significant asymmetry was observed in Begg's funnel plot in all studies.

CONCLUSION

RPT has favorable efficacy profiles in GIST patients, but the adverse reactions are obvious, and patient management needs to be strengthened to achieve better safety and tolerability.

Transcatheter arterial chemoembolization with tyrosine kinase inhibitor in the 12-year treatment of hepatic metastases from gastrointestinal stromal tumor: a case report

Background

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the digestive tract, with surgery and tyrosine kinase inhibitor (TKI) therapy being its main treatment options. However, long-term use of TKIs may lead to drug resistance, which poses a challenge to the long-term survival of patients. We explore a new combination of transcatheter arterial chemoembolization (TACE) with TKI for liver metastasis (LM) of GIST to provide patients with more treatment options and better prognosis.

Case Description

This case report describes the application of 6 TACE sessions in the 12-year treatment of multiple LM from small intestinal stromal tumors that were resistant to multiple TKIs. The patient, a 58-year-old male, underwent multiple surgical resections and drug therapies for the LM after a primary small bowel stromal tumor had been identified and resected following an onset symptom of abdominal pain in February 2012. Despite the challenges of drug resistance and economic considerations, 6 TACE sessions effectively controlled the tumor, winning valuable treatment time for the patient. Since the initiation of ripretinib 150 mg once daily in July 2023, the tumor has continued to shrink, with satisfactory drug tolerance.

Conclusions

For GIST patients with LM, TACE combined with various TKI drugs could effectively control intrahepatic tumor progression and prolong patient survival. During six TACE sessions, the patient experienced liver tumor rupture and massive bleeding. However, the bleeding was completely stopped by embolization, and the lesion shrank. Our findings provide a new perspective and treatment strategy for the treatment of LM from GIST.

Precision Oncology in Soft Tissue Sarcomas and Gastrointestinal Stromal Tumors

Soft tissue sarcomas (STSs), including gastrointestinal stromal tumors (GISTs), are mesenchymal neoplasms with heterogeneous clinical behavior and represent broad categories comprising multiple distinct biologic entities. Multidisciplinary management of these rare tumors is critical. To date, multiple studies have outlined the importance of biological characterization of mesenchymal tumors and have identified key molecular alterations which drive tumor biology. GIST has represented a flagship for targeted therapy in solid tumors with the advent of imatinib which has revolutionized the way we treat this malignancy. Herein, the authors discuss the importance of biological and molecular diagnostics in managing STS and GIST patients.

Efficacy and Safety of Ripretinib in Advanced Gastrointestinal Stromal Tumors within an Expanded Access Program: A Cohort Study

Ripretinib, a novel tyrosine kinase inhibitor used in advanced gastrointestinal stromal tumors (GIST) resistant to standard therapies, was assessed in the United Kingdom (UK) within an Expanded Access Program (EAP). A retrospective review of patients treated between January 2020 and October 2021 within the ripretinib EAP in our Institution was conducted. Clinician-documented and mRECIST 1.1 assessments were collected. The primary endpoints were progression-free survival (PFS) and time to treatment discontinuation (TTD). Treatment beyond progression (TBP), overall survival (OS), objective response rates and safety data were also analyzed. Survival curves were constructed using the Kaplan-Meier method, and univariate and multivariate Cox regression analyses were performed. All analyses were performed with R software. Overall, forty-five patients were included. After a median follow-up of 24.2 (95% CI 19.7-29.7) months, the median PFS of the group receiving 150 mg ripretinib once daily (OD) was 7.9 (95% CI 5.6-19.3) months. In the cohort of 22 patients with dose escalation upon tumor progression to 150 mg ripretinib twice daily (BD), the median PFS from BD was 5.4 (95% CI 2.8-9.3) months. Overall, median PFS and OS values for patients on ripretinib were 9.7 (95% CI 8.3-18.1) and 14.0 (95% CI 9.9-NA) months, respectively. TTD was similar to PFS. TBP was observed in about one third of all patients. Objective responses to ripretinib OD and BD treatments were observed in 16.7% and 10.0% of the patients, respectively. No new safety signals were identified. In conclusion, patients with advanced GIST receiving ripretinib in the UK within the EAP reported prolonged benefits, in line with the recent phase III clinical trials.

Outcomes of Late-Line Systemic Treatment in GIST: Does Sequence Matter?

Ripretinib and avapritinib have demonstrated activity in the late-line treatment of gastrointestinal stomal tumors (GISTs). We investigated whether patients previously treated with ripretinib benefit from avapritinib, and vice versa. Patients diagnosed with metastatic/unresectable GIST and treated with both drugs at two institutions in 2000-2021 were included. Patients were grouped by drug sequence: ripretinib-avapritinib (RA) or avapritinib-ripretinib (AR). Radiographic response was evaluated using RECIST 1.1. Kaplan-Meier and log-rank tests were used to compare time-to-progression (TTP) and overall survival (OS). Thirty-four patients (17 per group) were identified, with a median age of 48 years. The most common primary site was the small bowel (17/34, 50%), followed by the stomach (10/34, 29.4%). Baseline characteristics and tumor mutations were not significantly different between groups. Response rates (RRs) for ripretinib were 18% for RA and 12% for AR; RRs for avapritinib were 12% for AR and 18% for RA. Median TTPs for ripretinib were 3.65 months (95%CI 2-5.95) for RA and 4.73 months (1.87-15.84) for AR. Median TTPs for avapritinib were 5.39 months (2.86-18.99) for AR and 4.11 months (1.91-11.4) for RA. Median OS rates following RA or AR initiation were 29.63 (95%CI 13.8-50.53) and 33.7 (20.03-50.57) months, respectively. Both ripretinib and avapritinib were efficacious in the late-line treatment of GIST, with no evidence that efficacy depended on sequencing.

Multi-disciplinary management of recurrent gastrointestinal stromal tumor harboring KIT exon 11 mutation with the switch-control kinase inhibitor ripretinib and surgery

Ripretinib is a tyrosine kinase inhibitor that was approved by the United States FDA in 2020 for treatment of advanced gastrointestinal stromal tumor (GIST) in patients who received prior treatment with three or more tyrosine kinase inhibitors. In this case report, we show the durable clinical benefit achieved in a patient with GIST by using ripretinib and repeated timely surgical resection of limited disease progression. The total time on ripretinib was 43 months which is longer than the current reported data from ripretinib clinical trials. Such approach for using multi-disciplinary disease management can improve the durability of response to tyrosine kinase inhibitors, including ripretinib, and associated clinical outcomes.

Molecular Advances in the Treatment of Advanced Gastrointestinal Stromal Tumor

Most gastrointestinal stromal tumors (GIST) are driven by activating mutations in Proto-oncogene c-KIT (KIT) or PDGFRA receptor tyrosine kinases (RTK). The emergence of effective therapies targeting these mutations has revolutionized the management of advanced GIST. However, following initiation of first-line imatinib, a tyrosine kinase inhibitor (TKI), nearly all patients will develop resistance within 2 years through the emergence of secondary resistance mutations in KIT, typically in the Adenosine Triphosphate (ATP)-binding site or activation loop of the kinase domain. Moreover, some patients have de novo resistance to imatinib, such as those with mutations in PDGFRA exon 18 or those without KIT or PDGFRA mutation. To target resistance, research efforts are primarily focused on developing next-generation inhibitors of KIT and/or PDGFRA, which can inhibit alternate receptor conformations or unique mutations, and compounds that impact complimentary pathogenic processes or epigenetic events. Here, we review the literature on the medical management of high-risk localized and advanced GIST and provide an update on clinical trial approaches to this disease.

Molecular Tailored Therapeutic Options for Advanced Gastrointestinal Stromal Tumors (GISTs): Current Practice and Future Perspectives

Gastrointestinal stromal tumors (GISTs) are one of the most common mesenchymal tumors characterized by different molecular alterations that lead to specific clinical presentations and behaviors. In the last twenty years, thanks to the discovery of these mutations, several new treatment options have emerged. This review provides an extensive overview of GISTs’ molecular pathways and their respective tailored therapeutic strategies. Furthermore, current treatment strategies under investigation and future perspectives are analyzed and discussed.

Emerging Data on the Safety and Efficacy of Ripretinib for the Treatment of Gastrointestinal Stromal Tumors

In patients with gastrointestinal stromal tumors (GIST), systemic treatment after disease progression on imatinib is challenging. Sunitinib and regorafenib are approved in the second- and third-line setting, respectively, with activity against certain secondary mutations with comparatively much lower response rates and survival increment compared to imatinib. All three of these drugs were serendipitously found to have activity in GIST, starting with imatinib, which was formulated for its ability to inhibit BCR-ABL in chronic myelogenous leukemia. Ripretinib is a drug that was specifically developed as a more potent KIT tyrosine kinase inhibitor (TKI), with broad-spectrum activity against the mutations encountered in GIST. Encouraging responses in early and later lines of treatment in the Phase 1 trial of ripretinib in GIST led to the rapid development of this novel drug. In a Phase 3 randomized clinical trial with cross-over, ripretinib demonstrated superior PFS and overall survival (OS) in 4th-line treatment and beyond compared to placebo. This established 150 mg once daily ripretinib as the standard of care in this setting. Ripretinib is generally well tolerated, with common adverse effects of hair loss, diarrhea, cramps, fatigue and nausea. The favorable safety profile and efficacy of ripretinib prompted its evaluation in a randomized phase 3 trial in the 2nd-line treatment setting. However, it did not result in a longer PFS duration than sunitinib. Although the efficacy of ripretinib in this unselected patient population was not significantly different from that of sunitinib, the tolerability profile was better. This review article aims to review the efficacy and tolerability profile of ripretinib, together with its role in the setting of unresectable or metastatic GIST.

Ripretinib for the treatment of adult patients with advanced gastrointestinal stromal tumors

INTRODUCTION

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. Imatinib mesylate revolutionized the management of advanced/metastatic GIST, and remains the standard first-line therapy in this setting. Upon development of secondary resistance, sunitinib and regorafenib are used as subsequent treatments, although clinical benefit is often non-durable. Ripretinib is a type II kinase inhibitor targeting KIT and PDGFRA mutations and resistance through switching active I and inactive II forms.

AREAS COVERED

This drug profile article provides an overview of the current state of the art treatment algorithm for advanced/metastatic GIST, focusing on the role of ripretinib in the fourth-line setting as defined by currently available clinical trials evidence. The mechanism of action, the safety profile, efficacy, and clinical application of ripretinib are presented. In addition, the Phase I study (NCT02571036) through which the optimal dose was established and the Phase III trials that assessed the efficacy and safety of ripretinib as fourth- (INVICTUS) and second-line treatment (INTRIGUE) are presented.

EXPERT OPINION

Ripretinib is a safe and an effective therapy for the fourth-line setting in advanced/metastatic GIST. Future studies should evaluate combination schedules and the identification of markers predictive of benefit from ripretinib.

Insights into the medical management of gastrointestinal stromal tumours: lessons learnt from a dedicated gastrointestinal stromal tumour clinic in North India

Background

The advent of molecular driver alterations has brought in a revolutionary transformation in the treatment landscape of gastrointestinal stromal tumour (GIST). However, there is a paucity of data regarding mutational testing prevalence and associated outcomes from India.

Methods

It was a retrospective study. We reviewed the case records of all patients diagnosed with GIST in a tertiary care centre from 2015 to 2021. The clinicopathological, mutational analysis and treatment plans were recorded. The study cohort was characterised by descriptive statistics.

Results

Our study included 120 patients with a median age of 53 years (range: 28-77), with a male preponderance of 2:1. The most common site of the primary was the stomach (50%), followed by the small intestine (37%), with 55.8% of the patients having disseminated disease at presentation with a predominance of liver metastasis (67%). The prevalence of mutational analysis among patients prior to referral was 4%. 60.8% of the patients at our clinic had mutational analysis performed, and unavailability of analysis in the rest was due to financial constraints (12.5%), exhaustion of tissue (7.5%), reluctance to repeat biopsy (4.1%) and low-risk patients. We report c-kit in the majority (52%), platelet-derived growth factor receptor (PDGFR) in 19.2% and wild type in 16.4% along with the rarer subtypes: succinate dehydrogenase (SDH)-deficient GIST in 10.9% and Neurotrophic tyrosine receptor kinase (NTRK) fusion in 1.3%. Four of the eight SDH-deficient GIST patients had germline mutations (50%). The knowledge of driver mutations led to a change of treatment in 39.7% (29/73), i.e. stoppage of tyrosine kinase inhibitor (TKI) in 3, switch of TKI in 23, increase in TKI dose in 2 and upfront surgery in 1. The most common change was the use of sunitinib and regorafenib in patients with SDH-deficient GIST.

Conclusion

Our study is one of the largest comprehensive series describing the clinical and mutational profile of GIST from India. The mutation testing rates at primary care centres continue to be low. Despite the hurdles, a large percentage of our patients underwent molecular testing, aiding in therapeutic decision-making.

Patient-reported outcomes in individuals with advanced gastrointestinal stromal tumor treated with ripretinib in the fourth-line setting: analysis from the phase 3 INVICTUS trial

BACKGROUND

Ripretinib is a novel switch-control kinase inhibitor that inhibits KIT and PDGFRA signaling. In the INVICTUS phase 3 trial, ripretinib increased median progression-free survival and prolonged overall survival vs. placebo in ≥ fourth-line advanced GIST. Here, we report prespecified analysis of quality of life (QoL) as assessed by patient-reported outcome (PRO) measures and an exploratory analysis evaluating the impact of alopecia on QoL.

METHODS

In the INVICTUS trial (NCT03353753), QoL was assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30; physical function, role function, overall health, and overall QoL) and the EuroQoL 5-Dimension 5-Level (EQ-5D-5 L; visual analogue scale). Analysis of covariance (ANCOVA) models compared changes in scores from baseline to treatment cycle 2, day 1 within and between ripretinib and placebo. Within the ripretinib arm, repeated measures models assessed the impact of alopecia on QoL.

RESULTS

Patients receiving ripretinib maintained QoL (as assessed by the EORTC QLQ-C30 and EQ-5D-5 L PRO measures) from baseline to cycle 2, day 1 whereas QoL declined with placebo, resulting in clinically significant differences between treatments (nominal P < 0.01). The most common treatment-emergent adverse event with ripretinib was alopecia; however, QoL was similarly maintained out to treatment cycle 10, day 1 in patients receiving ripretinib who developed alopecia and those who did not.

CONCLUSION

PRO assessments in the INVICTUS trial suggest that patients on ripretinib maintain their QoL out to C2D1, unlike patients receiving placebo. Longitudinal QoL was maintained for patients receiving ripretinib out to cycle 10, day 1 (approximately 8 months; past the point of median progression-free survival with ripretinib [6.3 months]), even if the patients developed alopecia.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03353753 ; first posted: November 27, 2017.

Ripretinib Versus Sunitinib in Patients With Advanced Gastrointestinal Stromal Tumor After Treatment With Imatinib (INTRIGUE): A Randomized, Open-Label, Phase III Trial

PURPOSE

Sunitinib, a multitargeted tyrosine kinase inhibitor (TKI), is approved for advanced gastrointestinal stromal tumor (GIST) after imatinib failure. Ripretinib is a switch-control TKI approved for advanced GIST after prior treatment with three or more TKIs, including imatinib. We compared efficacy and safety of ripretinib versus sunitinib in patients with advanced GIST who were previously treated with imatinib (INTRIGUE, ClinicalTrials.gov identifier: NCT03673501).

PATIENTS AND METHODS

Random assignment was 1:1 to once-daily ripretinib 150 mg or once-daily sunitinib 50 mg (4 weeks on/2 weeks off) and stratified by KIT/platelet-derived growth factor α mutation and imatinib intolerance. The primary end point was progression-free survival (PFS) by independent radiologic review using modified Response Evaluation Criteria in Solid Tumors version 1.1. Secondary end points included objective response rate by independent radiologic review, safety, and patient-reported outcome measures.

RESULTS

Overall, 453 patients were randomly assigned to ripretinib (intention-to-treat [ITT], n = 226; KIT exon 11 ITT, n = 163) or sunitinib (ITT, n = 227; KIT exon 11 ITT, n = 164). Median PFS for ripretinib and sunitinib (KIT exon 11 ITT) was 8.3 and 7.0 months, respectively (hazard ratio, 0.88; 95% CI, 0.66 to 1.16; P = .36); median PFS (ITT) was 8.0 and 8.3 months, respectively (hazard ratio, 1.05; 95% CI, 0.82 to 1.33; nominal P = .72). Neither was statistically significant. Objective response rate was higher for ripretinib versus sunitinib in the KIT exon 11 ITT population (23.9% v 14.6%, nominal P = .03). Ripretinib was associated with a more favorable safety profile, fewer grade 3/4 treatment-emergent adverse events (41.3% v 65.6%, nominal P < .0001), and better scores on patient-reported outcome measures of tolerability.

CONCLUSION

Ripretinib was not superior to sunitinib in terms of PFS. However, meaningful clinical activity, fewer grade 3/4 treatment-emergent adverse events, and improved tolerability were observed with ripretinib.

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

Ripretinib is a switch control KIT kinase inhibitor approved for treatment of adults with advanced gastrointestinal stromal tumors who received prior treatment with 3 or more kinase inhibitors, including imatinib. Ripretinib and its active metabolite (DP-5439) are cleared mainly via cytochrome P450 enzyme 3A4/5 (CYP3A4/5), and ripretinib solubility is pH-dependent, thus the drug-drug interaction potentials of ripretinib with itraconazole (strong CYP3A inhibitor), rifampin (strong CYP3A inducer), and pantoprazole (proton pump inhibitor) were each evaluated in open-label, fixed-sequence study designs. Overall, 20 participants received ripretinib 50 mg alone and with itraconazole 200 mg once daily, 24 participants received ripretinib 100 mg alone and with rifampin 600 mg once daily, and 25 participants received ripretinib 50 mg alone and with pantoprazole 40 mg once daily. Ripretinib exposure increased with concomitant itraconazole, with geometric least-squares (LS) mean ratios of ripretinib area under the concentration-time curve from 0 to ∞ (AUC_0-∞ ) and maximum observed concentration (C_max ) of 199% and 136%. Ripretinib exposure decreased with concomitant rifampin: geometric LS mean ratios for ripretinib AUC_0-∞ and C_max were 39% and 82%. Pantoprazole coadministration had no effect on ripretinib pharmacokinetics. No unexpected safety signals occurred. No dose adjustment is required for ripretinib coadministered with gastric acid reducers and strong CYP3A inhibitors; patients also receiving strong CYP3A inhibitors should be monitored more frequently for adverse reactions. Concomitant ripretinib use with strong CYP3A inducers should be avoided. Prescribers should refer to approved labeling for specific dose recommendations with concomitant use of strong and moderate CYP3A inducers.

An overview of agents and treatments for PDGFRA-mutated gastrointestinal stromal tumors

Platelet-derived growth factor receptor A (PDGFRA) mutations occur in approximately 10-15% of gastrointestinal stromal tumors (GISTs). These tumors with PDGFRA mutations have a different pathogenesis, clinical characteristics, and treatment response compared to tumors with receptor tyrosine kinase protein (KIT) mutations (60-70%). Many clinical studies have investigated the use of tyrosine kinase inhibitors mainly in patients with KIT mutations; however, there is a lack of attention to the PDGFRA-mutated molecular subtype. The main effective inhibitors of PDGFRA are ripretinib, avapritinib, and crenolanib, and their mechanisms and efficacy in GIST (as confirmed in clinical trials) are described in this review. Some multi-targeted tyrosine kinase inhibitors with inhibitory effects on this molecular subtype are also introduced and summarized in this paper. This review focuses on PDGFRA-mutated GISTs, introduces their clinical characteristics, downstream molecular signaling pathways, and existing resistance mechanisms. We focus on the most recent literature that describes the development of PDGFRA inhibitors and their use in clinical trials, as well as the potential benefits from different combination therapy strategies.

Efficacy and Safety of Ripretinib in Chinese Patients with Advanced Gastrointestinal Stromal Tumors as a Fourth- or Later-Line Therapy: A Multicenter, Single-Arm, Open-Label Phase II Study

PURPOSE

This is a phase II multicenter, single-arm, open-label study assessing the efficacy, safety, and pharmacokinetics (PK) of ripretinib in Chinese patients with advanced gastrointestinal stromal tumor (GIST) as a fourth- or later-line therapy. It was designed to show consistency with the phase III INVICTUS study.

PATIENTS AND METHODS

Patients with disease progression on (or intolerance to) prior imatinib, sunitinib, and at least one other drug were recruited to receive ripretinib 150 mg once daily continuously in 28-day cycles. The primary endpoint was progression-free survival (PFS) based on independent radiologic review (IRR). Secondary efficacy endpoints included objective response rate (ORR) based on IRR and overall survival. Safety endpoints included the incidence and severity of adverse events (AE).

RESULTS

Between April 2020 and August 2020, 39 patients were enrolled. All were included in the safety analysis while 38 were included in the efficacy analysis. By primary data cut-off (February 26, 2021), the median PFS [90% confidence interval (CI)] was 7.2 (2.9-7.3) months; the lower bound of the 90% CI exceeded 1 month, fulfilling the standard of bridging success. The ORR (95% CI) based on IRR was 18.4% (7.7%-34.3%). Treatment-related treatment-emergent AEs (TRAE) were reported in 37 (94.9%) patients. The majority of TRAEs were of grade 1/2. A total of 6 patients (15.4%) experienced grade 3/4 TRAEs.

CONCLUSIONS

The results demonstrated that ripretinib can clinically improve the outcomes of Chinese patients with advanced GIST as a fourth- or later-line therapy. The efficacy, safety, and PK profiles of ripretinib are consistent with those in the global patient population.

Ripretinib in advanced gastrointestinal stromal tumors: an overview of current evidence and drug approval

Over the past 20 years, the management of gastrointestinal stromal tumors has acted as an important model in the advancement of molecularly targeted therapies for solid tumors. The success of imatinib has established it as a lasting therapy in the management of early-stage and advanced disease in the first-line setting. Imatinib resistance inevitably develops, resulting in the need for further lines of therapy. Ripretinib is an orally administered switch-control tyrosine kinase inhibitor, specifically developed to target both primary and secondary KIT and PDGFRα resistance mutations. Herein, the authors discuss the molecular rationale, the preclinical evidence and the clinical use of ripretinib in the treatment of gastrointestinal stromal tumors in the advanced stages of disease.

New Drug Approvals for Sarcoma in the Last 5 Years

Sarcoma and locally aggressive connective tissue tumors are a complex group of diseases with a growing number of histotypes in the most recent WHO classification. Most of these tumors are rare (incidence <6/10⁵/y) or ultrarare (<1/10⁶/y). Despite their rarity, sarcomas are often good models for the development of personalized medicine, and a large number of new clinical trials in select histotypes and molecular subsets were reported during the past 5 years, leading to a faster rate of new drug approvals. We analyzed the published literature and the abstracts reported in major congresses dedicated to sarcoma and connective tissue tumor management in the last 5 years. Several targeted therapies, cytotoxic treatments, and immunotherapies have demonstrated activity in dedicated histologic and molecular subtypes of sarcomas. The majority of the studies for ultrarare entities are uncontrolled studies, as a consequence of the rarity of histotypes, but randomized controlled trials were available in the less rare histotypes. Most successful trials were based on biomarker selection, which were often driver molecular alterations, while a large number of ongoing research programs aim to identify biomarkers in parallel to new drug development. Availability of the new agents varies across countries. This article describes the new drugs that made it through to the finish line and new agents with promising activity that are in later stages of investigation in the large family of malignant connective tissue tumors.

Efficacy and safety of ripretinib in patients with KIT-altered metastatic melanoma

BACKGROUND

Ripretinib, a broad-spectrum KIT and platelet-derived growth factor receptor A switch-control tyrosine kinase inhibitor, is approved for the treatment of adult patients with advanced gastrointestinal stromal tumor as ≥ fourth-line therapy. We present the efficacy and safety of ripretinib in patients with KIT-altered metastatic melanoma enrolled in the expansion phase of the ripretinib phase I study.

PATIENTS AND METHODS

Patients with KIT-altered metastatic melanoma were enrolled and treated with ripretinib at the recommended phase II dose of 150 mg once daily in 28-day cycles. Investigator-assessed responses according to Response Evaluation Criteria In Solid Tumors version 1.1 were carried out on day 1 of cycles 3, 5, 7, every three cycles thereafter, and at a final study visit.

RESULTS

A total of 26 patients with KIT-altered metastatic melanoma (25 with KIT mutations, 1 with KIT-amplification) were enrolled. Patients had received prior immunotherapy (n = 23, 88%) and KIT inhibitor therapy (n = 9, 35%). Confirmed objective response rate (ORR) was 23% [95% confidence interval (CI) 9%-44%; one complete and five partial responses] with a median duration of response of 9.1 months (range, 6.9-31.3 months). Median progression-free survival (mPFS) was 7.3 months (95% CI 1.9-13.6 months). Patients without prior KIT inhibitor therapy had a higher ORR and longer mPFS (n = 17, ORR 29%, mPFS 10.2 months) than those who had received prior KIT inhibitor treatment (n = 9, ORR 11%, mPFS 2.9 months). The most common treatment-related treatment-emergent adverse events (TEAEs) of any grade in ≥15% of patients were increased lipase, alopecia, actinic keratosis, myalgia, arthralgia, decreased appetite, fatigue, hyperkeratosis, nausea, and palmar-plantar erythrodysesthesia syndrome. There were no grade ≥4 treatment-related TEAEs.

CONCLUSIONS

In this phase I study, ripretinib demonstrated encouraging efficacy and a well-tolerated safety profile in patients with KIT-altered metastatic melanoma, suggesting ripretinib may have a clinically meaningful role in treating these patients.