The MOTION study: a randomized, phase III study of vimseltinib for the treatment of tenosynovial giant cell tumor

Tenosynovial giant cell tumor (TGCT) is a rare, locally aggressive neoplasm that occurs in the synovium of joints, bursae, or tendon sheaths and is caused by upregulation of the CSF1 gene. Vimseltinib is an oral switch-control tyrosine kinase inhibitor specifically designed to selectively and potently inhibit the CSF1 receptor. Here, we describe the rationale and design for the phase III MOTION trial (NCT05059262), which aims to evaluate the efficacy and safety of vimseltinib in participants with TGCT not amenable to surgical resection. In part 1, participants are randomized to receive vimseltinib 30 mg twice weekly or matching placebo for ≤24 weeks. Part 2 is a long-term treatment phase in which participants will receive open-label vimseltinib.

Ripretinib versus sunitinib in gastrointestinal stromal tumor: ctDNA biomarker analysis of the phase 3 INTRIGUE trial

INTRIGUE was an open-label, phase 3 study in adult patients with advanced gastrointestinal stromal tumor who had disease progression on or intolerance to imatinib and who were randomized to once-daily ripretinib 150 mg or sunitinib 50 mg. In the primary analysis, progression-free survival (PFS) with ripretinib was not superior to sunitinib. In clinical and nonclinical studies, ripretinib and sunitinib have demonstrated differential activity based on the exon location of KIT mutations. Therefore, we hypothesized that mutational analysis using circulating tumor DNA (ctDNA) might provide further insight. In this exploratory analysis (N = 362), baseline peripheral whole blood was analyzed by a 74-gene ctDNA next-generation sequencing-based assay. ctDNA was detected in 280/362 (77%) samples with KIT mutations in 213/362 patients (59%). Imatinib-resistant mutations were found in the KIT ATP-binding pocket (exons 13/14) and activation loop (exons 17/18). Mutational subgroup assessment showed 2 mutually exclusive populations with differential treatment effects. Patients with only KIT exon 11 + 13/14 mutations (ripretinib, n = 21; sunitinib, n = 20) had better PFS with sunitinib versus ripretinib (median, 15.0 versus 4.0 months). Patients with only KIT exon 11 + 17/18 mutations (ripretinib, n = 27; sunitinib, n = 25) had better PFS with ripretinib versus sunitinib (median, 14.2 versus 1.5 months). The results of this exploratory analysis suggest ctDNA sequencing may improve the prediction of the efficacy of single-drug therapies and support further evaluation of ripretinib in patients with KIT exon 11 + 17/18 mutations. ClinicalTrials.gov identifier: NCT03673501.

Patient-reported outcomes and tolerability in patients receiving ripretinib versus sunitinib after treatment with imatinib in INTRIGUE, a phase 3, open-label study

PURPOSE

In the INTRIGUE trial, ripretinib showed no significant difference versus sunitinib in progression-free survival for patients with advanced gastrointestinal stromal tumour (GIST) previously treated with imatinib. We compared the impact of these treatments on health-related quality of life (HRQoL).

PATIENTS AND METHODS

Patients were randomised 1:1 to once-daily ripretinib 150 mg or once-daily sunitinib 50 mg (4 weeks on/2 weeks off). Patient-reported outcomes were assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire for Cancer-30 (EORTC QLQ-C30) questionnaire at day (D)1, and D29 of all cycles until treatment discontinuation. Change from baseline was calculated. Time without symptoms or toxicity (TWiST) was estimated as the mean number of days without progression, death, or grade ≥3 treatment-emergent adverse events per patient over 1 year of follow-up.

RESULTS

Questionnaire completion at baseline was 88.1% (199/226) for ripretinib and 87.7% (199/227) for sunitinib and remained high for enrolled patients throughout treatment. Patients receiving sunitinib demonstrated within-cycle variation in self-reported HRQoL, corresponding to the on/off dosing regimen. Patients receiving ripretinib reported better HRQoL at D29 assessments than patients receiving sunitinib on all scales except constipation. HRQoL was similar between treatments at D1 assessments, following 2 weeks without treatment for sunitinib patients. TWiST was greater for ripretinib patients (173 versus 126 days).

CONCLUSION

Patients receiving ripretinib experienced better HRQoL than patients receiving sunitinib during the dosing period and similar HRQoL to patients who had not received sunitinib for 2 weeks for all QLQ-C30 domains except constipation. Ripretinib may provide clinically meaningful benefit to patients with advanced GIST previously treated with imatinib.

Mutational heterogeneity of imatinib resistance and efficacy of ripretinib vs sunitinib in patients with gastrointestinal stromal tumor: ctDNA analysis from INTRIGUE

397784

Background: Ripretinib, a switch-control tyrosine kinase inhibitor (TKI), is indicated for patients (pts) with gastrointestinal stromal tumor (GIST) who received prior treatment with ≥3 TKIs, including imatinib. Sunitinib is approved for advanced GIST after imatinib failure. Circulating tumor DNA (ctDNA) analysis may provide insight into the efficacy of these agents in second-line advanced GIST. Here, we present exploratory baseline ctDNA results from INTRIGUE. Methods: INTRIGUE is an open-label, phase 3 study that enrolled adult pts with advanced GIST who progressed on or had intolerance to imatinib (NCT03673501). Randomization was 1:1 to ripretinib 150 mg once daily (QD) or sunitinib 50 mg QD (4 wks on/2 wks off). Baseline peripheral whole blood was analyzed by Guardant360, a 74-gene ctDNA next-generation sequencing (NGS)-based assay. Only KIT mutations are reported here. Results: Of 453 pts in the overall intent-to-treat (ITT) population, 362 (80%) samples were analyzed. ctDNA was detected in 280/362 (77%), with KIT mutations detected in 213/280 (76%). Common resistance mutations were in the KIT activation loop (AL; exons 17/18; 89/213, 42%) and ATP-binding pocket (ATP-BP; exons 13/14; 81/213, 38%). Efficacy in pts with detectable ctDNA in the KIT exon 11 and overall ITT populations was consistent with the primary analysis based on tumor data used for randomization. Pts with KIT exon 11 + 17/18 (−9/13/14) mutations had superior progression-free survival (PFS), objective response rate (ORR), and overall survival (OS) with ripretinib vs sunitinib, whereas pts with exon 11 + 13/14 (−9/17/18) mutations had better PFS, ORR, and OS with sunitinib vs ripretinib (Table). Subgroup safety profiles were consistent with the primary analysis. Conclusions: While KIT ATP-BP mutations predicted clinical benefit from sunitinib vs ripretinib, pts harboring resistance mutations in the KIT AL derived meaningful clinical benefit from ripretinib but not sunitinib. This study demonstrates the value of ctDNA NGS-based sequencing of the complex landscape of KIT mutations to predict the clinical benefit of ripretinib or sunitinib as second-line therapy in pts with advanced GIST. Clinical trial information: NCT03673501 . [Table: see text]

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.

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.

A phase 1/2 study of DCC-3116 as a single agent and in combination with trametinib in patients with advanced or metastatic solid tumors with RAS or RAF mutations

TPS3178

Background: Autophagy, a catabolic process to resupply nutrients and recycle damaged organelles, is activated by cancer cells to survive hypoxia, limited nutrients, or chemotherapy. The RAS family of oncoproteins are the most commonly mutated oncoproteins in human cancer and require autophagy for tumor growth and survival. RAS activates signaling through the mitogen-activated protein kinase (MAPK) pathway that is responsible for regulating cell survival. ULK1/2 are kinases that receive and process input from nutrient and stress sensors to initiate autophagy. Inhibition of the MAPK pathway releases tonic inhibition of ULK1/2 and triggers autophagy as a survival mechanism, suggesting that ULK1/2 may provide a promising therapeutic target. DCC-3116 is a potent and selective ULK inhibitor that showed preclinical antitumor activity in combination with the MAPK kinase inhibitor trametinib (Smith et al. 2019 AACR-NCI-EORTC Poster). Here, we describe the Phase 1 study of DCC-3116 monotherapy and combination therapy with trametinib in patients with RAS or RAF mutant advanced or metastatic solid tumors. Methods: This is a Phase 1/2, multicenter, open-label, first-in-human study evaluating safety, tolerability, clinical activity, pharmacokinetics, and pharmacodynamics of DCC-3116 as a single agent and in combination with trametinib (NCT04892017). The study consists of single agent and combination dose escalation cohorts and expansion of combinations with demonstrated safety. Single-agent oral DCC-3116 will be administered twice daily (BID) in escalating cohorts in 28-day cycles until the recommended Phase 2 dose (RP2D) is determined. Subsequently, the single-agent RP2D or one level below the maximum tolerated dose (MTD) will be administered in combination with trametinib. Participants in the dose escalation phase must be ≥18 years with a histologically confirmed diagnosis of advanced or metastatic solid tumor with a documented RAS or RAF mutation, have progressed despite standard therapies, and have received ≥1 prior anticancer therapy. In the dose expansion phase, DCC-3116 will be given BID with trametinib in 28-day cycles to participants with pancreatic ductal adenocarcinoma, non-small cell lung cancer, colorectal cancer, or melanoma (Cohorts 1–4, respectively). Primary outcomes are incidence of adverse events, identification of MTD, and objective response rate per RECIST v1.1. Secondary outcomes include duration of response, clinical benefit rate, time to response, progression-free survival, and pharmacokinetic/pharmacodynamic attributes. Participants in dose expansion cohorts must be ≥18 years and meet cohort-specific criteria including histologically confirmed diagnoses, documented mutation status, and number of prior lines of systemic therapy. This study is recruiting and plans to enroll up to 130 participants. Clinical trial information: NCT04892017.

Patient reported outcomes and tolerability in patients receiving ripretinib versus sunitinib after imatinib treatment in INTRIGUE: A phase 3 open-label study

11541

Background: Ripretinib (R) is a switch-control tyrosine kinase inhibitor (TKI) indicated for the treatment of patients (pts) with advanced gastrointestinal stromal tumor (GIST) after prior treatment with ≥3 TKIs. In the INTRIGUE study (NCT03673501) there was no significant difference in median PFS (primary endpoint) between R and sunitinib (S). We present exploratory analyses of tolerability data and selected pt reported outcomes (PROs). Methods: Pts were randomized 1:1 to R 150 mg QD or S 50 mg QD 4 weeks on/2 weeks off.Dose modification was allowed for toxicity management. The event of interest was severe or life-threatening (grade ≥3) treatment-related adverse event prior to progression (sTRAE). Days with at least one sTRAE were summed for all treated pts and for pts with ≥1 sTRAE event. PROs were assessed using questions from EORTC QLQ-C30 and Dermatology Life Quality Index (DLQI) at cycle 1 (C1) day 1 (D1), D15, and D29; D1 and D29 of all other cycles; as well as at end of treatment. Differences in PRO scores between baseline and later assessments were calculated across visits. Long-term data will be presented. Results: Pts receiving R (n = 223) versus (vs) S (n = 221) experienced fewer sTRAEs (24% vs 51%, respectively). For all treated pts, the mean time with sTRAEs was 11 days for R and 42 days for S (ratio 0.27, P<0.0001). For pts with ≥1 sTRAE, the mean number of days with a sTRAE was 48 days for R vs 81 days for S (ratio 0.59, p = 0.037). Completion of PRO assessments across the two treatment arms was similar (baseline: R [n = 199], S [n = 199]; C1 D29: R [n = 167], S [n = 177]). Significant differences in self-reported functioning and symptoms were observed by C1 D29. For PROs relating to commonly reported sTRAEs, except constipation, pts in the R arm reported better outcomes than pts in the S arm. Pts in the R arm reported significantly (p<0.05) less decline compared to baseline in pt-reported role function as well as less increase, or improvement, in symptoms of fatigue, appetite loss, diarrhea, nausea/vomiting, and pain vs pts in the S arm. Moderate or severe effect of skin toxicity on pt life, as measured by DLQI in the R arm (n = 165) and in the S arm (n = 175), was observed in 6.6% of pts in the R arm vs 14.8% of pts in the S arm (p = 0.015). Conclusions: In the INTRIGUE study the total number of days with sTRAEs was fewer for pts receiving R vs S. Pts in the R arm also reported significantly less decline in pt-reported role function and less increase in symptoms related to commonly reported sTRAEs, except constipation, vs pts in the S arm. Medical writing provided by Costello Medical. Clinical trial information: NCT03673501.

MOTION: A randomized, phase 3, placebo-controlled, double-blind study of vimseltinib (DCC-3014) for the treatment of tenosynovial giant cell tumor

TPS11590

Background: Tenosynovial giant cell tumor (TGCT) is a rare, locally aggressive neoplasm that occurs in the synovium of joints, bursae, or tendon sheaths. TGCT is caused by upregulation of the colony-stimulating factor 1 (CSF1) gene, resulting in aberrant CSF1 expression and the recruitment of CSF1 receptor (R)-dependent inflammatory cells. Resection is the primary treatment, but nonsurgical treatment options are necessary for patients with symptomatic TGCT not amenable to surgical resection. Vimseltinib is an oral switch control TKI specifically designed to selectively and potently inhibit CSF1R. In a Phase 1/2 study in patients with TGCT, vimseltinib showed encouraging antitumor activity with an overall objective response rate (ORR) of 42% in the cohort receiving 30 mg twice weekly (recommended phase 2 dose; Gelderblom et al, ESMO 2021 Poster). Vimseltinib was also well tolerated, and the majority of the common (≥15%) treatment-emergent adverse events (TEAEs) were Grades 1–2. Among these common TEAEs, the only Grade 3–4 event in the Phase 2, twice-weekly, 30-mg cohort was increased blood creatine phosphokinase (CPK); however, this elevated CPK was not associated with any symptoms (Gelderblom et al, ESMO 2021 Poster). Phase 1/2 efficacy and safety data support further development of vimseltinib; here, we describe the ongoing Phase 3 study for patients with TGCT not amenable to surgical resection. Methods: MOTION (NCT05059262) is a Phase 3, randomized, placebo-controlled, double-blind study that aims to evaluate the efficacy and safety of vimseltinib for the treatment of TGCT not amenable to surgical resection. Participants must be at least 18 years of age and have histologically confirmed and symptomatic TGCT for which surgical resection will potentially cause worsening functional limitation or severe morbidity. Prior CSF1R therapy is not permitted (previous imatinib and nilotinib is allowed). In Part 1 of the study, eligible participants will be randomized 2:1 to receive either vimseltinib 30 mg twice a week or matched placebo for 24 weeks. The primary outcome measure is ORR assessed by central read using Response Evaluation Criteria in Solid Tumors version 1.1 at 25 weeks. Secondary outcome measures include ORR per tumor volume score, range of motion, and patient-reported outcomes. Participants assigned to placebo in Part 1 will have the option to receive vimseltinib in Part 2, a long-term treatment phase in which participants will receive open-label vimseltinib. This international study plans to randomize 120 participants and is currently enrolling. Clinical trial information: NCT05059262.

Effect of hepatic impairment on the pharmacokinetics of ripretinib

e16031

Background: Ripretinib is a tyrosine kinase inhibitor indicated for the treatment of patients with advanced gastrointestinal stromal tumor who have received prior treatment with ≥3 kinase inhibitors, including imatinib. Ripretinib and its active metabolite (DP-5439) are CYP3A substrates and coadministration with itraconazole (CYP3A inhibitor) increased exposure to each analyte by ̃100%. Therefore, we studied ripretinib in subjects with varying degrees of hepatic impairment (HI). Methods: Subjects with mild, moderate, and severe HI based on Child-Pugh, and matched healthy subjects received a single oral dose of ripretinib (50 mg, fasting) with 8 days of PK sampling. Concentrations of ripretinib and DP-5439 in plasma were measured by a liquid chromatography–tandem mass spectrometry (LC-MS/MS) assay. PK parameters were calculated using Phoenix WinNonlin, and the geometric least squares mean ratios and corresponding 90% confidence intervals of Cmax, AUC0-t, and AUC0-∞ (total and unbound) were calculated. Unbound concentrations were assessed at Tmax and 24 hours postdose. Results: Eight subjects with mild HI, 8 with moderate HI, 4 with severe HI, and 13 healthy matches were enrolled. As shown in the table, total ripretinib and DP-5439 PK was comparable for mild HI vs. healthy matches. For moderate HI, total ripretinib AUC was ̃100% higher (Cmax was comparable), whereas DP-5439 AUC was marginally higher (Cmax was 32% lower). For severe HI, total ripretinib AUC0-t was ̃160% higher and Cmax was ̃24% lower, whereas DP-5439 AUCs were ̃50% lower and Cmax was 78% lower. Unbound fraction was < 0.6% for ripretinib and 0.2-1.4% for DP-5439, with no clear trend with HI severity. The safety profile in HI subjects was similar to healthy matches; common adverse events (in ≥2 subjects) included increased lipase or amylase, diarrhea, and headache. Conclusions: Consistent with current labeling, mild HI had no impact on total PK. In this study, moderate and severe HI increased ripretinib AUC ̃100% and 163%, respectively. PK exposure to DP-5439 and combined ripretinib + DP-5439 was impacted to a lesser extent. Dose recommendations in moderate and severe HI are currently under development.[Table: see text]

INTRIGUE: A phase III, randomized, open-label study to evaluate the efficacy and safety of ripretinib versus sunitinib in patients with advanced gastrointestinal stromal tumor previously treated with imatinib

359881

Background: Sunitinib is approved for advanced gastrointestinal stromal tumor (GIST) after imatinib failure. Ripretinib, a broad-spectrum KIT and PDGFRA switch-control tyrosine kinase inhibitor (TKI), is indicated for the treatment of adult patients (pts) with GIST who received prior treatment with 3 or more TKIs, including imatinib. We compared the efficacy and safety of ripretinib vs sunitinib in pts with advanced GIST who progressed on or were intolerant to imatinib. Methods: This multicenter, global, randomized, open-label phase 3 study (NCT03673501) enrolled adult pts with GIST who progressed on or had intolerance to imatinib. Pts were randomized 1:1 to ripretinib 150 mg once daily (QD) or sunitinib 50 mg QD (4 wks on/2 wks off). Randomization was stratified by KIT mutational status and imatinib intolerance. The primary endpoint was progression-free survival (PFS) by independent radiologic review (IRR) using modified RECIST version 1.1. Key secondary endpoints were objective response rate (ORR) by IRR and overall survival (OS). Hierarchical testing was performed for primary and key secondary endpoints in a prespecified sequence; testing pts with a KIT exon 11 primary mutation (Ex11 intention-to-treat [ITT] population) preceded the all-patient (AP) ITT population. Data cutoff was 1 Sep 2021; final analyses of PFS and ORR and the first interim analysis of OS were conducted. Results: A total of 453 pts were randomized to ripretinib (n = 226; Ex11 ITT, n = 163) or sunitinib (n = 227; Ex11 ITT, n = 164). Median age was 60 yrs (range 18–88) and most pts were white (66.2%) males (62.0%). PFS was not statistically different between ripretinib and sunitinib in the Ex11 ITT (hazard ratio [HR] 0.88, 95% CI 0.66, 1.16; P = 0.36; median 8.3 vs 7.0 mos) or in the AP populations (HR 1.05, 95% CI 0.82, 1.33; P = 0.72; median 8.0 vs 8.3 mos). ORR was numerically higher for ripretinib vs sunitinib in the Ex11 ITT (23.9% vs 14.6%; difference 9.3%, 95% CI 0.7, 17.8; nominal P = 0.03) and AP ITT populations (21.7% vs 17.6%; difference 4.2%, 95% CI −3.2, 11.5; nominal P = 0.27). OS data was highly immature; median OS was not reached in either arm. Fewer pts in the ripretinib arm experienced Grade 3-4 (G3-4) treatment-emergent adverse events (TEAEs) vs sunitinib (41.3% vs 65.6%). Among G3-4 TEAEs with a difference ≥5% between arms, ripretinib had fewer events vs sunitinib (hypertension [8.5% vs 26.7%], palmar-plantar erythrodysesthesia [1.3% vs 10.0%], neutropenia [0% vs 6.3%], and neutrophil count decreased [0% vs 7.2%]). Conclusions: The PFS in both arms was longer than PFS achieved by sunitinib in its pivotal phase 3 trial. While the PFS for ripretinib did not meet the primary endpoint of superiority vs sunitinib, meaningful clinical activity and fewer G3-4 TEAEs were observed in pts with advanced GIST treated with ripretinib after imatinib failure. Clinical trial information: NCT03673501.

Clinical Activity of Ripretinib in Patients with Advanced Gastrointestinal Stromal Tumor Harboring Heterogeneous KIT/PDGFRA Mutations in the Phase III INVICTUS Study

PURPOSE

Most patients with gastrointestinal stromal tumor (GIST) have activating mutations in KIT/PDGFRA and are initially responsive to tyrosine kinase inhibitors (TKI). The acquisition of secondary mutations leads to refractory/relapsed disease. This study reports the results of an analysis from the phase III INVICTUS study (NCT03353753) characterizing the genomic heterogeneity of tumors from patients with advanced GIST and evaluating ripretinib efficacy across KIT/PDGFRA mutation subgroups.

PATIENTS AND METHODS

Tumor tissue and liquid biopsy samples that captured circulating tumor DNA were collected prior to study enrollment and sequenced using next-generation sequencing. Subgroups were determined by KIT/PDGFRA mutations and correlation of clinical outcomes and KIT/PDGFRA mutational status was assessed.

RESULTS

Overall, 129 patients enrolled (ripretinib 150 mg once daily, n = 85; placebo, n = 44). The most common primary mutation subgroup detected by combined tissue and liquid biopsies were in KIT exon 11 (ripretinib, 61.2%; placebo, 77.3%) and KIT exon 9 (ripretinib, 18.8%; placebo, 15.9%). Patients receiving ripretinib demonstrated progression-free survival (PFS) benefit versus placebo regardless of mutation status (HR 0.16) and in all assessed subgroups in Kaplan-Meier PFS analysis (exon 11, P < 0.0001; exon 9, P = 0.0023; exon 13, P < 0.0001; exon 17, P < 0.0001). Among patients with wild-type KIT/PDGFRA by tumor tissue, PFS ranged from 2 to 23 months for ripretinib versus 0.9 to 10.1 months for placebo.

CONCLUSIONS

Ripretinib provided clinically meaningful activity across mutation subgroups in patients with advanced GIST, demonstrating that ripretinib inhibits a broad range of KIT/PDGFRA mutations in patients with advanced GIST who were previously treated with three or more TKIs.

Vimseltinib: A Precision CSF1R Therapy for Tenosynovial Giant Cell Tumors and Diseases Promoted by Macrophages

Macrophages can be co-opted to contribute to neoplastic, neurologic, and inflammatory diseases. Colony-stimulating factor 1 receptor (CSF1R)-dependent macrophages and other inflammatory cells can suppress the adaptive immune system in cancer and contribute to angiogenesis, tumor growth, and metastasis. CSF1R-expressing osteoclasts mediate bone degradation in osteolytic cancers and cancers that metastasize to bone. In the rare disease tenosynovial giant cell tumor (TGCT), aberrant CSF1 expression and production driven by a gene translocation leads to the recruitment and growth of tumors formed by CSF1R-dependent inflammatory cells. Small molecules and antibodies targeting the CSF1/CSF1R axis have shown promise in the treatment of TGCT and cancer, with pexidartinib recently receiving FDA approval for treatment of TGCT. Many small-molecule kinase inhibitors of CSF1R also inhibit the closely related kinases KIT, PDGFRA, PDGFRB, and FLT3, thus CSF1R suppression may be limited by off-target activity and associated adverse events. Vimseltinib (DCC-3014) is an oral, switch control tyrosine kinase inhibitor specifically designed to selectively and potently inhibit CSF1R by exploiting unique features of the switch control region that regulates kinase conformational activation. In preclinical studies, vimseltinib durably suppressed CSF1R activity in vitro and in vivo, depleted macrophages and other CSF1R-dependent cells, and resulted in inhibition of tumor growth and bone degradation in mouse cancer models. Translationally, in a phase I clinical study, vimseltinib treatment led to modulation of biomarkers of CSF1R inhibition and reduction in tumor burden in TGCT patients.

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

PURPOSE

Ripretinib is a switch-control tyrosine kinase inhibitor that broadly inhibits KIT and platelet-derived growth factor receptor α kinase signalling. Ripretinib showed preliminary efficacy in patients with advanced gastrointestinal stromal tumour (GIST) in a phase I study across a range of doses. Results were confirmed in the phase III INVICTUS study, and ripretinib 150 mg once daily (QD) was subsequently approved as a ≥fourth-line therapy. Here, we report the phase I study results of intrapatient dose escalation (IPDE) in patients with GIST treated across second, third and later lines of therapy.

METHODS

Patients with advanced GIST who experienced disease progression (PD) at ripretinib 150 mg QD could dose escalate to 150 mg twice daily (BID). Progression-free survival (PFS) 1 was calculated from the date of the first dose of ripretinib 150 mg QD to PD (as per Response Evaluation Criteria in Solid Tumours 1.1); PFS2 was from the date of IPDE (150 mg BID) to PD or death. Treatment-emergent adverse events (TEAEs) were summarised by dosing periods and compared descriptively.

RESULTS

Of 142 patients with GIST receiving ripretinib 150 mg QD, 67 underwent IPDE. IPDE provided benefit across all lines of therapy; the median PFS2 was 5.6, 3.3 and 4.6 months for patients on second-, third- and ≥fourth-line therapy, respectively. A partial metabolic response after IPDE was demonstrated in 13 of 37 patients with available positron emission tomography scans. TEAEs reported at both doses were similar.

CONCLUSION

Ripretinib IPDE after PD provided continued clinical benefit in advanced GIST across second, third and later lines of therapy with a similar safety profile to that observed with the QD regimen.

Clinical Benefit of Ripretinib Dose Escalation After Disease Progression in Advanced Gastrointestinal Stromal Tumor: An Analysis of the INVICTUS Study

Background

Ripretinib 150 mg once daily (QD) is indicated for advanced gastrointestinal stromal tumors (GISTs) as at least fourth‐line therapy. In INVICTUS, ripretinib intrapatient dose escalation (IPDE) to 150 mg b.i.d. was allowed after progressive disease (PD) on 150 mg QD by blinded independent central review using modified RECIST 1.1. We report the efficacy and safety of ripretinib IPDE to 150 mg b.i.d. after PD among patients randomized to ripretinib 150 mg QD in the INVICTUS study.

Materials and Methods

Tumor imaging was performed every 28‐day cycle for the first four cycles in the ripretinib 150 mg QD period and then every other cycle, including the 150 mg b.i.d. period. Among the ripretinib IPDE patients, progression‐free survival (PFS)1 was the time from randomization until PD; PFS2 was the time from the first dose of ripretinib 150 mg b.i.d. to PD or death.

Results

Among 43 ripretinib IPDE patients, median PFS1 was 4.6 months (95% confidence interval [CI], 2.7–6.4) and median PFS2 was 3.7 months (95% CI, 3.1–5.3). Median overall survival was 18.4 months (95% CI, 14.5–not estimable). Ripretinib 150 mg b.i.d. (median duration of treatment 3.7 months) was well tolerated with new or worsening grade 3–4 treatment‐emergent adverse events (TEAEs) of anemia in six (14%) and abdominal pain in three (7%) patients. Ripretinib 150 mg b.i.d. was discontinued because of TEAEs in seven (16%) patients.

Conclusion

Ripretinib 150 mg b.i.d. after PD on 150 mg QD may provide additional clinically meaningful benefit with an acceptable safety profile in patients with at least fourth‐line GISTs.

Implications for Practice

Of the 85 patients with advanced gastrointestinal stromal tumor having received at least three prior anticancer therapies randomized to ripretinib 150 mg once daily (QD) in the phase III INVICTUS study, 43 underwent ripretinib intrapatient dose escalation (IPDE) to 150 mg b.i.d. after progressive disease (PD). Median progression‐free survival was 4.6 months before and 3.7 months after ripretinib IPDE. The safety profile of ripretinib 150 mg b.i.d. was acceptable. These findings indicate ripretinib IPDE to 150 mg b.i.d. may provide additional clinical benefit in patients with PD on ripretinib 150 mg QD, for whom limited treatment options exist.

This article presents further results from the INVICTUS study, focusing on patients who received ripretinib 150 mg QD who received intrapatient dose escalation to 150 mg b.i.d. after progressive disease.

Abstract CT123: Population pharmacokinetics of ripretinib in patients with advanced malignancies

Ripretinib is a tyrosine kinase inhibitor (TKI) indicated for the treatment of adult patients with advanced gastrointestinal stromal tumor (GIST) who have received prior treatment with 3 or more kinase inhibitors, including imatinib. In a phase 1 study (NCT02571036), the maximum tolerated dose was not reached at doses up to 200 mg twice daily (BID). Ripretinib 150 mg BID intrapatient dose escalation regimen was offered to patients in the phase 1 and 3 trials (INVICTUS, NCT03353753) after radiologic progression at 150 mg once daily (QD). The BID dose was well tolerated with a similar safety profile to the 150 mg QD (approved dose regimen). In this analysis, the population pharmacokinetics (popPK) of ripretinib and DP-5439, a metabolite TKI with in vitro activity and exposure similar to ripretinib, were characterized and potential covariates influencing exposure were evaluated. The popPK models were developed for ripretinib and DP-5439 using 5284 and 5160 quantifiable concentrations, respectively, from 350 patients pooled from the phase 1 and INVICTUS phase 3 studies. Models were estimated using first-order conditional estimation with interaction method in NONMEM® (version 7.3; ICON, Hanover, MD, USA) and evaluated based on standard goodness-of-fit metrics. A covariate analysis was conducted to assess the sources of variability in ripretinib pharmacokinetics (PK) using a full model approach with backward elimination (significance level = 0.005). Tested covariates included age, body weight, sex, race, tumor type, prior gastrectomy, and mild hepatic impairment and mild to moderate renal impairment. Ripretinib oral PK was well described by a 2-compartment model with zero-order drug release at the absorption site followed by first-order absorption with a modest, linear dose-dependent decrease in relative bioavailability and linear elimination. A high-fat meal was predicted to increase the ripretinib AUC by 36% at 150 mg QD relative to the fasted state. The only covariate effect retained in the final popPK model for ripretinib was 29% lower apparent clearance in females compared with males, resulting in a 40% higher AUC in females. No other covariates were identified for ripretinib. The resulting effect on DP-5439 was similar. PK exposure in patients with mild hepatic impairment or mild to moderate renal impairment was similar to that in patients with normal organ function. There were no clinically meaningful differences in the PK of ripretinib based on age, race, body weight, or tumor type. Based on the safety profile of ripretinib observed in patients with advanced GIST and PK variability, the effects of sex, fasted state, and prior gastrectomy on ripretinib PK were not considered clinically significant. Therefore, ripretinib can be taken with or without food by all patients and no dose adjustment is recommended for patients with mild hepatic impairment or patients with mild to moderate renal impairment.

Citation Format: Suzanne George, Filip Janku, Ping Chi, Margaret von Mehren, Neeta Somaiah, Hans Gelderblom, Robin L. Jones, Martine Allard, Adekemi Taylor, Xiaoyan Li, Julie Meade, Vienna Reichert, Rodrigo Ruiz-Soto, Jing Wang, Michael C. Heinrich. Population pharmacokinetics of ripretinib in patients with advanced malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT123.

Abstract CT132: Effect of gastric acid reduction and strong CYP3A induction/inhibition on the pharmacokinetics of ripretinib, a switch control tyrosine kinase inhibitor

Ripretinib is a tyrosine kinase inhibitor indicated for the treatment of adult patients with advanced gastrointestinal stromal tumor who have received prior treatment with 3 or more kinase inhibitors, including imatinib. In a phase 1 study in patients with advanced malignancies, the maximum tolerated dose was not reached at doses up to 200 mg twice daily (BID). Dose escalation to ripretinib 150 mg BID was offered in the phase 1 and phase 3 clinical studies after radiologic disease progression at 150 mg once daily (QD) and was well tolerated with a similar safety profile as seen with 150 mg QD (approved dose regimen). Ripretinib solubility is pH dependent and ripretinib and its active metabolite (DP-5439) are cleared via CYP3A4/5; thus, drug-drug interactions (DDIs) with acid-reducing agents and strong CYP3A inhibitors/inducers were assessed. Here, we report the effects of pantoprazole (proton pump inhibitor), itraconazole (strong CYP3A inhibitor) and rifampin (strong CYP3A inducer) on the pharmacokinetics (PK) of ripretinib and DP-5439. Ripretinib PK is generally dose proportional within 50-150 mg. For each interaction, single oral doses of ripretinib (either 50 mg for pantoprazole and itraconazole or 100 mg for rifampin) were given before and concurrently with multiple doses of each perpetrator agent to healthy volunteers: pantoprazole 40 mg QD x 7 days (n = 25), itraconazole 200 mg QD x 10 days (n = 20), and rifampin 600 mg QD x 14 days (n = 24). Serial blood samples were collected over 4-7 days before and after each perpetrator drug; plasma concentrations of ripretinib and DP-5439 were determined by validated LC-MS/MS. The geometric least-squares mean (GLSM) ratios of PK parameters (i.e., AUC0-∞ and Cmax) and corresponding 90% confidence intervals (CIs) were calculated. No DDI was observed between ripretinib and pantoprazole. The ratios of GLSM and 90% CIs for AUC0-∞ and Cmax were within the bioequivalence 80%−125% range for ripretinib with pantoprazole vs ripretinib alone. Concomitant itraconazole increased exposure to ripretinib and DP-5439; GLSM ratios for ripretinib AUC0-∞ and Cmax were 199% and 136%, respectively, and similar ratios were noted for DP-5439. Exposure to ripretinib and DP-5439 based on AUC0-∞ decreased with rifampin coadministration. GLSM ratios for ripretinib AUC0-∞ and Cmax were 39% and 82%, respectively, for ripretinib with rifampin vs ripretinib alone, and were 43% and 137% for DP-5439. No dose adjustments are required when ripretinib is coadministered with either gastric acid reducers or strong CYP3A inhibitors, based on the magnitude of DDI PK effects in healthy volunteers, and the safety profile of ripretinib observed in patients and healthy volunteers. However, as decreased exposure may reduce the antitumor activity of ripretinib, concomitant use of strong CYP3A inducers with ripretinib should be avoided.

Citation Format: Xiaoyan Li, Mark J. Shelton, Julie Meade, Cherie Taglienti, Constance Barysauskas, Rodrigo Ruiz-Soto, Jing Wang. Effect of gastric acid reduction and strong CYP3A induction/inhibition on the pharmacokinetics of ripretinib, a switch control tyrosine kinase inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT132.

Intra-patient dose escalation (IPDE) of ripretinib after disease progression in patients with advanced gastrointestinal stromal tumor (GIST): Analyses from the phase 3 INVICTUS study

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Background: Ripretinib is a switch-control tyrosine kinase inhibitor that broadly inhibits KIT and PDGFRA kinase signaling. In the INVICTUS study (NCT03353753), patients with advanced GIST (≥4th-line) receiving ripretinib had a median progression-free survival (mPFS) of 6.3 months vs 1.0 month for patients receiving placebo (HR = 0.15, p <0.0001). In an earlier phase 1 dose escalation study, the maximum tolerated dose was not reached with doses up to 200 mg twice daily (BID). Here, we report efficacy, safety, and pharmacokinetic data for IPDE patients initially randomized to ripretinib from the phase 3 INVICTUS study based on data as of 10 Aug 2020. Methods: A total of 129 patients were randomized 2:1 to ripretinib 150 mg once daily (QD; n = 85) or placebo (n = 44). Patients receiving ripretinib 150 mg QD who had progressive disease (PD) as assessed by blinded independent central review (BICR) using mRECIST were given the option for IPDE to 150 mg BID. Tumor response assessments were performed every 28 days for 4 cycles and every 56 days thereafter (including after IPDE). The primary endpoint was PFS. For this exploratory analysis, PFS1 for IPDE patients was defined as the time from randomization to PD; PFS2 for IPDE patients was the time from the first dose of ripretinib 150 mg BID to PD or death. PFS1 and PFS2 were based on BICR. Results: Of 85 patients treated with ripretinib 150 mg QD, 43 patients with BICR PD dose escalated to 150 mg BID. Baseline characteristics of IPDE patients at time of study entry were similar to those observed in the original ripretinib QD arm and similar to the 22 patients with BICR PD who either remained on 150 mg QD or discontinued treatment. IPDE patients had a mPFS1 of 4.6 months (95% CI, 2.7–6.4) and a mPFS2 of 3.7 months (95% CI, 3.1–5.3); mPFS2/mPFS1=80%. The IPDE dosing period was well tolerated without the emergence of new safety concerns. The most common new or worsening (unchanged or improving grades not included) treatment-emergent adverse event (TEAE) for IPDE patients during the BID period was abdominal pain (30.2% all grades and 7% Grade 3–4 vs 41.9% and 4.7% in QD period, respectively). The most common Grade 3–4 TEAE in the BID period was anemia (14% vs 2.3% in QD period). IPDE from QD to BID resulted in an approximately 2-fold increase in the steady state trough concentration. Conclusions: Similar to the phase 1 study wherein IPDE to 150 mg BID following PD provided clinical benefit with a mPFS1 of 5.5 months and mPFS2 of 4.6 months (mPFS2/mPFS1=84%) for patients with ≥4th-line GIST, these analyses from INVICTUS indicate that IPDE to ripretinib 150 mg BID can also provide additional meaningful clinical benefit and a similar tolerability profile to the 150 mg QD regimen for patients with ≥4th-line GIST that progressed following treatment with ripretinib 150 mg QD. Clinical trial information: NCT03353753.

Open-label, multicenter, phase 1b/2 study of rebastinib in combination with paclitaxel to assess safety and efficacy in patients with advanced or metastatic endometrial cancer

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Background: Rebastinib is a first-in-class investigational, orally administered, potent and selective switch-control kinase inhibitor of tunica interna endothelial cell kinase (TIE2). This is a 2-part open-label, multicenter Phase 1b/2 study of rebastinib in combination with paclitaxel. Here we provide updated results (ASCO 2020) from the fully enrolled endometrial cancer (EC) cohort of the study. Methods: Part 2 of the study has five disease-specific cohorts (EC, platinum-resistant ovarian cancer, gynecological carcinosarcoma, TNBC and inflammatory breast cancer). Patients were treated at the RP2D and evaluated for efficacy (RECIST v1.1) and safety (CTCAE v5.0). Results: As of Jan 8, 2021, 38 EC patients were enrolled (median age of 66 years); 42% were of grade 2/3 endometroid histological subtype. All patients received at least 1 prior line of paclitaxel in combination with carboplatin and 79% of patients received ≥3 prior anti-cancer regimens. Sixteen of 38 patients were initially treated with a starting dose of rebastinib 100 mg BID, 11 of which dose reduced to 50 mg BID, and 22 patients were treated with a starting dose of rebastinib 50 mg BID, in combination with paclitaxel 80 mg/m2 IV weekly (days 1, 8, 15 of 28-day cycle). In 33 evaluable patients with median follow-up of 5.9 months, the ORR was 33% and clinical benefit rate at 8 and 16 weeks was 70% and 55%, respectively, including 11 PRs (8 confirmed) and 12 SDs. Treatment-emergent adverse events ( > 20% of patients; mostly ≤ grade 2) included fatigue (n = 18), constipation, peripheral edema (each at n = 16), peripheral sensory neuropathy, nausea (each at n = 15), dyspnea (n = 13), alopecia, hypokalemia (each at n = 11), diarrhea, hypomagnesemia (each at n = 10), dry mouth, dysgeusia (each at n = 9), arthralgia, hypertension, dehydration, GERD and muscular weakness (each at n = 8). Serious adverse events (SAE) at least possibly related to rebastinib included muscular weakness (n = 2 at 100 mg BID, n = 1 at 50 mg BID), nausea (n = 2), acute myocardial infarction, atrial flutter, dehydration, non-infective encephalitis, peritonsillitis, and stress cardiomyopathy (each at n = 1) and were resolved after dose interruption. Conclusions: The updated results of rebastinib at 50 mg BID in combination with paclitaxel showed encouraging preliminary anti-tumor activity and an acceptable safety profile in heavily pretreated EC patients, and supports further development in patients with EC (NCT03601897). Clinical trial information: NCT03601897.

Switch Control Inhibition of KIT and PDGFRA in Patients With Advanced Gastrointestinal Stromal Tumor: A Phase I Study of Ripretinib

PURPOSE

In advanced gastrointestinal stromal tumor (GIST), there is an unmet need for therapies that target both primary and secondary mutations of pathogenic KIT/PDGFRA oncoproteins. Ripretinib is a novel switch-control kinase inhibitor designed to inhibit a wide range of KIT and PDGFRA mutations.

PATIENTS AND METHODS

This first-in-human, to our knowledge, phase I study of ripretinib (ClinicalTrials.gov identifier: NCT02571036) included a dose-escalation phase and subsequent expansion phase at the recommended phase II dose (RP2D). Eligible patients included those with advanced GIST, intolerant to or experienced progression on ≥ 1 line of systemic therapy, and other advanced malignancies. Safety, dose-limiting toxicities (DLTs), maximum-tolerated dose (MTD), and preliminary antitumor activity were evaluated.

RESULTS

At data cutoff (August 31, 2019), 258 patients (n = 184 GIST) were enrolled, with 68 patients in the dose-escalation phase. Three DLTs were reported: grade 3 lipase increase (n = 2; 100 mg and 200 mg twice a day) and grade 4 increased creatine phosphokinase (n = 1; 150 mg once daily). MTD was not reached (maximum dose evaluated, 200 mg twice a day); 150 mg once daily was established as the RP2D. The most frequent (> 30%) treatment-emergent adverse events in patients with GIST receiving ripretinib 150 mg once daily (n = 142) were alopecia (n = 88 [62.0%]), fatigue (n = 78 [54.9%]), myalgia (n = 69 [48.6%]), nausea (n = 65 [45.8%]), palmar-plantar erythrodysesthesia (n = 62 [43.7%]), constipation (n = 56 [39.4%]), decreased appetite (n = 48 [33.8%]), and diarrhea (n = 47 [33.1%]). Objective response rate (confirmed) of 11.3% (n = 16/142) ranging from 7.2% (n = 6/83; fourth line or greater) to 19.4% (n = 6/31; second line) and median progression-free survival ranging from 5.5 months (fourth line or greater) to 10.7 months (second line), on the basis of investigator assessment, were observed.

CONCLUSION

Ripretinib is a well-tolerated, novel inhibitor of KIT and PDGFRA mutant kinases with promising activity in patients with refractory advanced GIST.

Ripretinib in patients with advanced gastrointestinal stromal tumours (INVICTUS): a double-blind, randomised, placebo-controlled, phase 3 trial

BACKGROUND

Resistance to approved inhibitors of KIT proto-oncogene, receptor tyrosine kinase (KIT), and platelet-derived growth factor receptor α (PDGFRA) is a clinical challenge for patients with advanced gastrointestinal stromal tumours. We compared the efficacy and safety of ripretinib, a switch-control tyrosine kinase inhibitor active against a broad spectrum of KIT and PDGFRA mutations, with placebo in patients with previously treated, advanced gastrointestinal stromal tumours.

METHODS

In this double-blind, randomised, placebo-controlled, phase 3 study, we enrolled adult patients in 29 specialised hospitals in 12 countries. We included patients aged 18 years or older who had advanced gastrointestinal stromal tumours with progression on at least imatinib, sunitinib, and regorafenib or documented intolerance to any of these treatments despite dose modifications, and who had an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Eligible patients were randomly assigned (2:1) to receive either oral ripretinib 150 mg once daily (ripretenib group) or placebo once daily (placebo group). Randomisation was done via an interactive response system using randomly permuted block sizes of six and stratified according to number of previous therapies and ECOG performance status. Patients, investigators, research staff, and the sponsor study team were masked to a patient's treatment allocation until the blinded independent central review (BICR) showed progressive disease for the patient. The primary endpoint was progression-free survival, assessed by BICR. The primary analysis was done in the intention-to-treat population and safety was assessed in patients who received at least one dose of study drug. Patients randomly assigned to placebo were permitted to cross over to ripretinib 150 mg at the time of disease progression. The INVICTUS study is registered with ClinicalTrials.gov, number NCT03353753, and with WHO International Clinical Trials Registry Platform, number EUCTR2017-002446-76-ES; follow-up is ongoing.

FINDINGS

Between Feb 27, 2018, and Nov 16, 2018, 129 of 154 assessed patients were randomly assigned to receive either ripretinib (n=85) or placebo (n=44). At data cutoff (May 31, 2019), at a median follow-up of 6·3 months (IQR 3·2-8·2) in the ripretinib group and 1·6 months (1·1-2·7) in the placebo group, 51 patients in the ripretinib group and 37 in the placebo group had had progression-free survival events. In the double-blind period, median progression-free survival was 6·3 months (95% CI 4·6-6·9) with ripretinib compared with 1·0 months (0·9-1·7) with placebo (hazard ratio 0·15, 95% CI 0·09-0·25; p<0·0001). The most common (>2%) grade 3 or 4 treatment-related treatment-emergent adverse events in the ripretinib group (n=85) included lipase increase (four [5%]), hypertension (three [4%]), fatigue (two [2%]), and hypophosphataemia (two (2%]); in the placebo group (n=43), the most common (>2%) grade 3 or 4 treatment-related treatment-emergent adverse events were anaemia (three [7%]), fatigue (one [2%]), diarrhoea (one [2%]), decreased appetite (one [2%]), dehydration (one [2%]), hyperkalaemia (one [2%]), acute kidney injury (one [2%]), and pulmonary oedema (one [2%]). Treatment-related serious adverse events were reported in eight (9%) of 85 patients who received ripretinib and three (7%) of 43 patients who received placebo. Treatment-related deaths occurred in one patient in the placebo group (septic shock and pulmonary oedema) and one patient in the ripretinib group (cause of death unknown; the patient died during sleep).

INTERPRETATION

Ripretinib significantly improved median progression-free survival compared with placebo and had an acceptable safety profile in patients with advanced gastrointestinal stromal tumours who were resistant to approved treatments.

FUNDING

Deciphera Pharmaceuticals.

An open-label, multicenter, phase Ib/II study of rebastinib in combination with paclitaxel in a dose-expansion cohort to assess safety and preliminary efficacy in patients with advanced or metastatic endometrial cancer

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Background: Rebastinib is a switch control inhibitor targeting tunica interna endothelial cell kinase (TIE2). TIE2 is primarily expressed in endothelial cells playing a role in angiogenesis. TIE2 is also expressed in a subset of macrophages with pro-metastatic and immunosuppressive properties and linked to chemo-resistance. This study is a 2-part open-label, phase Ib/II, multicenter study of rebastinib orally administered, in combination with paclitaxel. In Part 1, we observed encouraging antitumor activity of rebastinib with 5 PRs in 24 patients (pts) at 50 mg BID and 3 PRs in 19 pts at 100 mg BID from a heavily pretreated heterogeneous patient population. Here we summarize preliminary results from the endometrial cancer (EC) cohort of Part 2. Methods: Part 2 of this study has four disease-specific cohorts (TNBC, inflammatory breast cancer, ovarian cancer and EC). Pts were evaluated for safety (CTCAE v5.0) and efficacy (RECIST v1.1). According to the Simon 2-stage design of this study, for each cohort, 15 additional pts will be enrolled if more than 4 PRs are observed. Results: As of Jan 21, 2020, 19 EC pts were enrolled with a median age of 66 years. All pts received at least one prior line of paclitaxel and 12 (63%) pts received >3 prior anti-cancer therapies. Sixteen pts were treated with rebastinib starting dose 100 mg BID (reduced to 50 mg BID due to a higher frequency of muscular weakness) and 3 pts with 50 mg BID, in combination with 80 mg/m2 weekly paclitaxel with a median duration of treatment 85 days (6, 225). In 15 evaluable pts, there were 5 PRs (4 confirmed) and 6 SD8 weeks for an ORR of 33% and clinical benefit rate of 73%. Treatment-emergent AEs (>20%) were mostly ≤ grade 2: constipation, fatigue (each n=9); alopecia, peripheral edema (each n=8); dysgeusia, peripheral sensory neuropathy, arthralgia (each n=6); diarrhea, hypomagnesaemia, vomiting, dry mouth (each n=5); anemia, decreased appetite, dyspnea, nausea, and muscular weakness (each n=4). Serious AEs possibly related or related to rebastinib included muscular weakness (n=2, at 100 mg BID), head discomfort (n=1) and increase troponin (n=1) which resolved after dose interruption. Conclusions: Preliminary activity of rebastinib in combination with paclitaxel was encouraging in heavily pretreated EC pts, all of whom received prior paclitaxel. The safety profile of rebastinib at 50 mg BID was generally well tolerated. The EC cohort is enrolling at 50 mg BID in stage 2 of the study. Clinical trial information: NCT03601897.

Quality of life (QoL) and self-reported function with ripretinib in ≥4th-line therapy for patients with gastrointestinal stromal tumors (GIST): Analyses from INVICTUS

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Background: Ripretinib is a novel switch-control tyrosine kinase inhibitor (TKI) that broadly inhibits KIT and PDGFRA kinase signaling through a dual mechanism of action. In INVICTUS (NCT03353753), a randomized, double-blind, placebo-controlled trial of ripretinib in ≥4th-line advanced GIST, ripretinib reduced the risk of disease progression or death by 85% vs placebo and had a favorable overall safety profile in patients previously treated with ≥3 prior TKIs. Methods: As part of the INVICTUS trial, patient reported outcome (PRO) measures were collected using EQ-5D-5L (EQ5D) and EORTC QLQ-C30 (C30). In prespecified and additional analyses, ANCOVA models were built to compare changes from baseline to cycle 2 day 1 (C2D1) for PRO measures within the ripretinib and placebo arms and determine the difference between treatment arms. PRO measures included the EQ5D visual analogue scale (VAS) and the C30 physical functioning (PF) and role functioning (RF) scales (all scores range from 0–100; higher scores are better). The C30 overall health and overall QoL questions were also assessed (scores range from 1–7; higher scores are better). Fixed effects included treatment arm, number of previous anticancer treatments (3 vs ≥4), and ECOG score at baseline (0 vs 1/2). Results: Overall, 129 patients were randomized and 128 received treatment (85 to ripretinib 150 mg QD; 43 to placebo). All PRO p-values are nominal, and no statistical significance is being claimed. VAS scores improved an average 3.7 points from baseline to C2D1 with ripretinib vs an average decline of 8.9 with placebo (P = 0.004; improvement or no change, 67% vs 41% of patients, respectively). Similarly, the average PF score improved 1.6 points with ripretinib and decreased 8.9 with placebo (P = 0.004; improvement or no change, 68% vs 44%). RF scores also improved an average of 3.5 points with ripretinib vs a decrease of 17.1 with placebo (P = 0.001; improvement or no change, 77% vs 50%). For the overall health and overall QoL questions, scores increased with ripretinib an average of 0.20 and 0.28, respectively, and decreased 0.78 and 0.76 with placebo (both P = 0.001; improvement or no change, 74% vs 47% and 79% vs 59%, respectively). Conclusions: Based on the 5 PRO measures assessed, when compared with placebo and best supportive care, ripretinib provided patient-benefit in advanced GIST with PRO measures of role and physical function, VAS, overall health, and overall QoL remaining stable. Clinical trial information: NCT03353753 .

Safety profile of ripretinib, including impact of alopecia, and Palmar-Plantar Erythrodysesthesia Syndrome (PPES) on patient-reported outcomes (PROs), in ≥ fourth-line advanced gastrointestinal stromal tumors (GIST): Analyses from INVICTUS

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Background: Ripretinib is a novel switch-control TKI that broadly inhibits KIT and PDGFRA kinase signaling. In INVICTUS (NCT03353753), a randomized, double-blind, placebo (PBO)-controlled trial of ripretinib in ≥4th-line advanced GIST, ripretinib reduced the risk of disease progression or death by 85% vs PBO with a favorable overall safety profile. Common ( > 20%) adverse events (AEs) included, but were not limited to, alopecia and PPES. Exploratory analyses evaluated the impact of alopecia and PPES on quality of life (QoL). Methods: Patients (pts) with advanced GIST previously treated with at least imatinib, sunitinib, and regorafenib were randomized (2:1) to ripretinib 150 mg QD or PBO. AEs were graded using CTCAE v4 and PROs collected using EQ-5D-5L (EQ5D) and EORTC QLQ-C30 (C30). Repeated measures (RM) models assessed the impact of alopecia and PPES on 5 PROs (EQ5D visual analogue scale; and C30 physical functioning, role functioning, and the overall health and overall QoL questions) within the ripretinib arm. Fixed effects were sex, alopecia/PPES, and ECOG scores at baseline. Results: 128/129 randomized pts received treatment (85 ripretinib 150 mg QD; 43 PBO). Alopecia, regardless of causality, occurred in 44 (51.8%) on ripretinib (34 [40.0%] grade 1; 10 [11.8%] grade 2) and 2 (4.7%) on PBO (both grade 1). PPES occurred in 18 (21.2%) on ripretinib (11 [12.9%] grade 1; 7 [8.2%] grade 2); none on PBO. The median times in days to first occurrence and worst severity grade with ripretinib were 57.0 and 62.5 for alopecia; 56.5 and 57.0 for PPES. The RM models showed a slight trend towards improvement in PRO score over time for pts with alopecia; the only association reaching a P-value of < 0.05 was between alopecia and increased overall QoL. None of the associations between PPES and PRO scores reach P < 0.05. All PRO p-values are nominal, and no statistical significance is being claimed. Conclusions: Ripretinib had a favorable overall safety and tolerability profile. When stratified by alopecia and PPES, patient-reported assessments of function, overall health, and overall QoL were maintained over time. For both alopecia and PPES, onset and maximum severity occurred almost simultaneously, indicating that these events generally did not progressively worsen. These results suggest that alopecia and PPES are manageable and do not have a negative effect on function, overall health, and QoL. Clinical trial information: NCT03353753 .

Intrigue: Phase III study of ripretinib versus sunitinib in advanced gastrointestinal stromal tumor after imatinib

Ripretinib (DCC-2618) is a novel, type II tyrosine switch control inhibitor designed to broadly inhibit activating and drug-resistant mutations in KIT and PDGFRA. Ripretinib has emerged as a promising investigational agent for the treatment of gastrointestinal stromal tumor owing to targeted inhibition of secondary resistance mutations that may develop following treatment with prior line(s) of tyrosine kinase inhibitors. Here we describe the rationale and design of intrigue (NCT03673501), a global, randomized (1:1), open-label, Phase III study comparing the safety and efficacy of ripretinib versus sunitinib in patients with advanced gastrointestinal stromal tumor following imatinib. The primary end point is progression-free survival and key secondary objectives include objective response rate and overall survival. Clinical Trial Registration: NCT03673501.

Abstract B055: Phase 1b/2 study of rebastinib (DCC-2036) in combination with paclitaxel: Preliminary safety, efficacy, pharmacokinetics and pharmacodynamics in patients with advanced or metastatic solid tumors

Background: Rebastinib is an orally administered, kinase inhibitor targeting the switch pocket of tunica interna endothelial cell kinase (TIE2). TIE2 is primarily expressed in endothelial cells, playing a role in angiogenesis. In addition, TIE2 is expressed in a subset of macrophages, TIE2 expressing macrophages (TEMs), which have pro-angiogenic, pro-metastatic, and immunosuppressive properties. Accumulating evidence suggests that chemotherapies, such as paclitaxel, increase the recruitment and activity of TEMs, leading to chemotherapy resistance. This study aims to investigate the efficacy of anti-TIE2 therapy against chemo-resistant advanced solid tumors. Methods: This is an open-label, Phase 1b/2, multicenter study with two parts. Part 1 evaluated two doses of rebastinib at 50 and 100 mg twice daily (BID) with paclitaxel administered weekly at 80 mg/m2 to determine the recommended phase 2 dose (RP2D) by enrolling at least 15 pts in each arm. The objective of Part 1 is to identify a recommended Phase 2 dose. Pts with locally advanced or metastatic solid tumors for which paclitaxel was considered appropriate treatment were enrolled. Part 2 has four disease-specific cohorts: triple-negative breast cancer, inflammatory breast cancer, platinum-resistant ovarian cancer and metastatic endometrial cancer to further evaluate the safety, tolerability and efficacy of the RP2D. This abstract focuses on data from Part 1. Results: A total of 43 pts were enrolled in Part 1 (24 pts at 50 mg BID and 19 pts at 100 mg BID) as of June 21, 2019. The median age was 61 years; 79% were female. Most frequent diagnoses were ovarian (11 pts), breast (8 pts) and endometrial cancer (7 pts). The median number of prior anti-cancer therapies was four (4). Median duration of treatment is 56 days. Treatment-emergent adverse events (TEAEs) were reported for 41 pts. Most TEAEs were previously observed in the rebastinib first-in-human study or were known AEs of paclitaxel. TEAEs &gt;10% include mostly Grade (Gr) 1 or 2 fatigue (30%), constipation (21%), dry mouth (21%), nausea and alopecia (19% each), anemia and UTI (16%), hypokalemia, hypomagnesemia, peripheral neuropathy, and dyspnea (14% each), diarrhea, stomatitis, vomiting, sepsis, dysgeusia, rash and ALT elevation (12% each). Twenty-four pts experienced at least one ≥Gr 3 TEAE. Six pts had ≥Gr 3 AEs related to rebastinib. No significant difference in TEAEs was observed between the two dose levels. The RP2D was determined for rebastinib at 100 mg BID in combination with weekly paclitaxel at 80 mg/m2. Exposure of rebastinib was dose-proportional. Plasma TIE2 and its ligand, ANG2, were induced in a dose-dependent manner. Evidence of observed preliminary clinical activity in heavily pre-treated patients will be presented. Conclusion: Preliminary results demonstrated that the combination of rebastinib and paclitaxel was generally well tolerated. This combination is currently under evaluation in four disease-specific cohorts in Part 2. Clinical trial information: NCT03601897.

Citation Format: Filip Janku, Michael Birrer, Debra Richardson, Christina Chu, Sanjay Goel, Ying Su, Bahar Matin, Keisuke Kuida, Rodrigo Ruiz-Soto, Erika Paige Hamilton. Phase 1b/2 study of rebastinib (DCC-2036) in combination with paclitaxel: Preliminary safety, efficacy, pharmacokinetics and pharmacodynamics in patients with advanced or metastatic solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr B055. doi:10.1158/1535-7163.TARG-19-B055

Abstract C087: Phase 1 study of DCC-3014, an oral inhibitor of CSF1R, to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics in patients with advanced solid tumors, including diffuse-type tenosynovial giant cell tumor

Background: DCC-3014 is an orally administered kinase inhibitor targeting the switch pocket of colony-stimulating factor 1 receptor (CSF1R). DCC-3014 exhibits approximately 100-fold selectivity from kinases homologous to CSF1R, such as KIT, and greater selectivity against 300 other human kinases. Tumor-associated macrophages (TAMs) are dependent on CSF1R kinase activity for proliferation and maintenance of the immunosuppressive phenotype. TAMs are known to enable tumor cells escape from immune surveillance. DCC-3014 is designed to exhibit an antitumor effect by inhibition of immunosuppressive TAMs or other CSF1R signaling-dependent pro-tumor activities. In addition, tenosynovial giant cell tumor (TGCT) is a rare, monoarticular disease known to be caused by the translocation in the CSF1 gene leading to overexpression of CSF1. Anti-CSF1R therapies have shown clinical activity in diffuse TGCT. Methods: This study is a multicenter, first-in-human study of DCC-3014 to determine a recommended Phase 2 dose (RP2D) or maximally tolerated dose (MTD) with a 3+3 dose escalation design and evaluate the safety, efficacy, pharmacokinetics (PK) and pharmacodynamics (PD) of DCC-3014 in advanced solid tumors, including diffuse-type TGCT [NCT03069469]. Results: As of June 2, 2019, the study is ongoing in the dose escalation phase and has enrolled 32 patients with advanced solid tumors in 7 cohorts. The first cohort was initiated at 10 mg daily. Based on preliminary PK analysis from the first cohort, subsequent cohorts utilized a loading dose followed by a maintenance dosing schedule to achieve steady-state exposures more rapidly. The median age of patients was 61 years old and 69% were female with the median of 4 lines of prior anti-cancer treatment. No dose limiting toxicities (DLTs) have been seen in the assessed cohorts. Most commonly seen treatment-emergent adverse events (TEAEs &gt;20%) were constipation (38%), vomiting (34%), diarrhea (31%), nausea (31%), decreased appetite (25%), abdominal pain (22%), and dyspnea (22%) whereas diarrhea, nausea and fatigue were reported as treatment-related AEs seen in &gt;10% of all patients (13%). TEAEs were mostly Grade 1 or 2. Serious AEs (SAEs) were seen in 16 patients, none of which were related to DCC-3014. Exposure was approximately dose proportional. PD effects were seen for dose levels at 10 mg and above, and induction of the CSF1R ligand, CSF-1, was seen up to 148-fold from baseline. The RP2D or MTD has not been selected or reached. Conclusion: DCC-3014 in this study was generally well tolerated in patients with advanced solid tumors and showed approximately dose-proportional exposure and PD changes as expected. Further evaluation is ongoing to determine the RP2D or MTD. Data from the TGCT cohort will be presented at a future meeting.

Citation Format: Matthew H Taylor, Stephen Leong, Ying Su, Cynthia B Leary, Xiaoyan Li, Keisuke Kuida, Rodrigo Ruiz-Soto, Todd Bauer. Phase 1 study of DCC-3014, an oral inhibitor of CSF1R, to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics in patients with advanced solid tumors, including diffuse-type tenosynovial giant cell tumor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C087. doi:10.1158/1535-7163.TARG-19-C087

Abstract C077: Updated results of phase 1 study of ripretinib (DCC-2618), a broad-spectrum KIT and PDGFRA inhibitor, in patients with gastrointestinal stromal tumor (GIST) by line of therapy (NCT02571036)

Objective: Ripretinib (DCC-2618) is a kinase switch control inhibitor designed to broadly inhibit KIT and PDGFRA mutations. Based on clinical activity observed in heavily pretreated patients (pts) with GIST in a Phase 1 study (NCT02571036), ripretinib is under evaluation in two Phase 3 studies: INVICTUS (NCT03353753) in ≥4th-line pts and INTRIGUE (NCT03673501) in 2nd-line pts, each at the recommended dose of 150 mg once daily (QD). This abstract reports updated results from the escalation and expansion phases of the Phase 1 study for pts treated with ≥100 mg daily dose. Methods: The Phase 1 study includes a dose-escalation phase that tested oral ripretinib QD or twice daily (BID) in 28-day cycles, followed by an expansion phase with the recommended Phase 2 dose (RP2D) of 150 mg QD in 6 cohorts, including cohorts for pts with GIST based on prior regimens (2nd/ 3rd, 4th, and &gt;4th-line). Local Response Evaluation Criteria in Solid Tumors (RECIST) response assessments were performed every 2 cycles and pts who progressed per RECIST in the expansion cohorts were allowed to dose escalate to 150 mg BID. Results: At a cut-off date of March 01, 2019, 179 pts with GIST in the escalation and expansion phases (median follow-up of 10.4 months; range, 0.1–32.3) were enrolled at dose levels of ≥100 mg daily with KIT-driven (169 pts), PDGFRA-driven (9 pts), or wild-type-driven GIST (1 pt). Of 178 pts with GIST treated at the ≥100 mg daily dose (1 pt was not included in the intent-to-treat population as the pt only participated in the food effect portion of the study), there were 37 2nd-line pts, 31 3rd-line pts, 60 4th-line pts, and 50 &gt;4th-line pts. The objective response rate (ORR) by best response was 30% in 2nd-line pts (n=11; includes 3 unconfirmed responses), 23% in 3rd-line pts (n=7; includes 3 unconfirmed responses), and 11% in ≥4th-line pts (n=12; includes 4 unconfirmed responses); responses ≥4th-line include 15% in 4th-line pts (n=9; includes 4 unconfirmed responses) and 6% in &gt;4th-line pts (n=3; includes no unconfirmed responses). In 2nd-line pts, the disease control rate (DCR) was 31% (n=9) at 52 weeks. The median progression-free survival (mPFS) was 42 weeks in 2nd-line pts, 40 weeks in 3rd-line pts, and 24 weeks in ≥4th-line pts (includes 30 weeks in 4th-line pts and 16 weeks in &gt;4th-line pts). In 2nd-line pts, the median duration of response was 80 weeks and the median duration of treatment was 44 weeks. For any line, 13% of pts (n=24) experienced treatment-emergent adverse events (TEAEs) leading to study treatment discontinuation, 17% of pts (n=31) experienced TEAEs leading to dose reduction and 49% (n=88) had TEAEs leading to study drug interruption. Grade 3 or 4 TEAEs in &gt;5% of pts were lipase increased (18%; n=33), anemia (11%; n=20), hypertension (7%; n=13), and abdominal pain (6%; n=11). Conclusion: In this Phase 1 study, ripretinib demonstrated encouraging clinical benefit (as measured by mPFS, ORR [best response] and DCR) and was generally well-tolerated in pts with GIST treated in the 2nd-line or later. Preliminary data from this Phase 1 study further supports testing in the ongoing Phase 3 study in 2nd-line GIST.

Citation Format: Ping Chi, Filip Janku, Michael Heinrich, Kristen Ganjoo, Hans Gelderblom, Michael Gordon, Robin Jones, Albiruni Razak, Jonathan Trent, Margaret von Mehren, Simin Hu, Ying Su, Rodrigo Ruiz-Soto, Suzanne George. Updated results of phase 1 study of ripretinib (DCC-2618), a broad-spectrum KIT and PDGFRA inhibitor, in patients with gastrointestinal stromal tumor (GIST) by line of therapy (NCT02571036) [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C077. doi:10.1158/1535-7163.TARG-19-C077

Abstract CT058: Ripretinib (DCC-2618) pharmacokinetics (PK) in a Phase I study in patients with gastrointestinal stromal tumors (GIST) and other advanced malignancies: A retrospective evaluation of the PK effects of proton pump inhibitors (PPIs)

Objectives: Ripretinib is a novel, oral kinase switch control inhibitor of KIT and PDGFRα. Encouraging clinical benefit from the phase 1 dose escalation and expansion study as measured by ORR, DCR and PFS in 2nd, 3rd, and &gt;4th line GIST patients with a favorable tolerability profile at doses &gt;100 mg/day has been previously reported (ESMO 2018, abstract #1603O). It has been reported that more than 40% of GIST patients use acid-reducing agents. PPIs are the most potent acid-reducing agents that may impair the absorption of kinase inhibitors 1,2. This retrospective analysis aims to explore whether ripretinib can be used regardless of concomitant PPI use.

Methods: The analysis assessed the impact of PPIs on the plasma concentration of ripretinib using PK data from the expansion cohort at the recommended Phase 2 dose of 150 mg QD. Plasma concentrations of ripretinib and its active metabolite DP-5439 obtained from patients who used or did not use PPIs were compared on Cycle 1 Day 1 (C1D1, n=106) and Day 15 (C1D15, n=102). Patients using PPIs were defined as those who continuously took PPIs for at least 4 days prior to C1D1 or C1D15. Patients who did not use PPIs were defined as those who did not take PPIs or any other acid-reducing agents during the study.

Results: PK profiles were consistent between patients using and not using PPIs (Table 1), indicating a low likelihood of a clinically significant drug interaction between PPIs and ripretinib.

Conclusions: This retrospective PK analysis provides supporting evidence that restriction of co-administration of PPIs with ripretinib may not be necessary. A dedicated drug interaction study is planned to provide a definitive assessment. References: 1. Smelick et al, Mol. Pharmaceutics 2013, 10, 4055−4062 2. Budha et al, Clin Pharmacol Ther. 2012, 92(2):203-13

Table 1.PK Exposure of Ripretinib and DP-5439 in Patients Using or not Using PPIsPK ConcentrationsRipretinib in ng/mL [mean (CV%)]DP-5439 in ng/mL [mean (CV%)]Ripretinib + DP-5439 in ng/mL [mean (CV%)]Using PPIsNot using PPIsUsing PPIsNot using PPIsUsing PPIsNot using PPIsC1D1 6 hr566 (58%) n=24670 (53%) n=82302 (64%) n=23297 (59%) n=82862 (54%) n=24975 (48%) n=82C1D15 pre-dose364 (79%) n= 24344 (63%) n=78960 (80%) n=24889 (86%) n=781350 (72%) n=241260 (75%) n=78C1D15 6 hr834 (51%) n=24871 (47%) n=731170 (69%) n=241060 (67%) n=732040 (53%) n=241960 (49%) n=73Notes: Table 1 is based on data from patients without a history of gastrectomy. A separate analysis in patients with gastrectomy will be published after sufficient data is obtained.

Citation Format: Filip Janku, Michael Heinrich, Ping Chi, Albiruni Abdul Razak, Margaret von Mehren, Michael Gordon, Kristen Ganjoo, Jonathan Trent, Robin L. Jones, Hans Gelderblom, Kelli Running, Jing Wang, Rodrigo Ruiz-Soto, Suzanne George. Ripretinib (DCC-2618) pharmacokinetics (PK) in a Phase I study in patients with gastrointestinal stromal tumors (GIST) and other advanced malignancies: A retrospective evaluation of the PK effects of proton pump inhibitors (PPIs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT058.

An open label, multicenter, phase 1b/2 study of rebastinib (DCC-2036) in combination with carboplatin to assess safety, tolerability, and pharmacokinetics in patients with advanced or metastatic solid tumors

TPS2666

Background: Rebastinib is a potent, orally administered, kinase switch control inhibitor selectively targeting the tunica interna endothelial cell kinase (TIE2). TIE2 is primarily expressed in endothelial cells and has critical roles in angiogenesis. In addition, TIE2 is highly expressed in a subset of macrophages, TIE2-expressing macrophages (TEMs), which are known to have proangiogenic, pro-metastatic, and immunosuppressive properties. Accumulating evidence suggests that chemotherapies, such as carboplatin, increase the recruitment and activity of pro-tumoral TEMs, leading to chemotherapy resistance. Taken together, investigation of rebastinib in combination with a chemotherapy such as carboplatin, one of the most commonly used agents across different tumor types, is warranted in advanced solid tumors. Methods: This study is an open-label, Phase 1b/2, multicenter study in patients with advanced or metastatic solid tumors. The study has two parts: the first part is the 3+3 dose escalation phase designed to evaluate the safety, tolerability and pharmacokinetics of 50 mg and 100 mg rebastinib twice daily in combination with carboplatin of AUC 5 or 6 administered once every three weeks to determine the recommended phase 2 dose (RP2D). Patients who have exhausted all therapies and for whom carboplatin is considered appropriate treatment will be enrolled. The second part is the dose expansion phase with three cohorts: previously treated breast cancer, recurrent, platinum-sensitive ovarian cancer, and malignant mesothelioma to evaluate the safety, tolerability, and efficacy of the RP2D. A Simon’s two-stage design will be used in the second part and initially up to 18 patients will be enrolled into each cohort. If more than 4 responses are observed, then the cohort will be expanded up to 33 patients. This trial is expected to enroll up to 117 patients in total, with approximately 18 patients in the first part and up to 99 patients in the second part. The study is currently open only in the US. Clinical trial information: NCT03717415.

Ripretinib (DCC-2618) Is a Switch Control Kinase Inhibitor of a Broad Spectrum of Oncogenic and Drug-Resistant KIT and PDGFRA Variants

Ripretinib (DCC-2618) was designed to inhibit the full spectrum of mutant KIT and PDGFRA kinases found in cancers and myeloproliferative neoplasms, particularly in gastrointestinal stromal tumors (GISTs), in which the heterogeneity of drug-resistant KIT mutations is a major challenge. Ripretinib is a "switch-control" kinase inhibitor that forces the activation loop (or activation "switch") into an inactive conformation. Ripretinib inhibits all tested KIT and PDGFRA mutants, and notably is a type II kinase inhibitor demonstrated to broadly inhibit activation loop mutations in KIT and PDGFRA, previously thought only achievable with type I inhibitors. Ripretinib shows efficacy in preclinical cancer models, and preliminary clinical data provide proof-of-concept that ripretinib inhibits a wide range of KIT mutants in patients with drug-resistant GISTs.

Characterization of folate receptor alpha (FRα) expression in archival tumor and biopsy samples from relapsed epithelial ovarian cancer patients: A phase I expansion study of the FRα-targeting antibody-drug conjugate mirvetuximab soravtansine

PURPOSE

To characterize folate receptor alpha (FRα) expression in archival and fresh biopsy tumor samples from relapsed ovarian cancer patients.

METHODS

Patients with ovarian tumors amenable to biopsy were eligible to enroll. Eligibility included a minimum requirement of FRα positivity in archival tumor samples (≥25% of cells with ≥2+ staining intensity). Patients received mirvetuximab soravtansine at 6mg/kg once every 3weeks. Core needle biopsies were collected before and after treatment and FRα levels assessed by immunohistochemistry. Descriptive statistics were used to summarize the association between receptor expression and response.

RESULTS

Twenty-seven heavily pre-treated patients were enrolled. Six individuals (22%) did not have evaluable pre-treatment biopsies due to insufficient tumor cells. The concordance of FRα expression in archival and biopsy tissues was 71%, and no major shifts in receptor expression were seen in matched pre- and post-treatment biopsy samples. Adverse events were generally mild (≤grade 2) with keratopathy (48%), fatigue (44%), diarrhea, and blurred vision (each 37%) being the most common treatment-related toxicities. The confirmed objective response rate (ORR) was 22%, including two complete responses and four partial responses. Superior efficacy measures were observed in the subset of patients with the highest FRα levels (ORR, 31%; progression-free survival, 5.4months).

CONCLUSION

Concordance of FRα expression in biopsy versus archival tumor samples suggests that archival tissue can reliably identify patients with receptor-positive tumors and is appropriate for patient selection in mirvetuximab soravtansine clinical trials. Regardless of the tissue source analyzed, higher FRα expression was associated with greater antitumor activity.

Mirvetuximab soravtansine (IMGN853), a folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC), in platinum-resistant epithelial ovarian cancer (EOC) patients (pts): Activity and safety analyses in phase I pooled expansion cohorts

5547

Background: The early clinical evaluation of mirvetuximab soravtansine (IMGN853), an ADC that comprises a FRα-binding antibody linked to the tubulin-disrupting maytansinoid DM4, has revealed encouraging signs of activity in pts with ovarian cancer. A pooled analysis of safety and efficacy was performed including individuals with platinum-resistant EOC, enrolled across three expansion cohorts of an ongoing phase I trial (NCT01609556), who met the eligibility criteria for the pivotal phase III study of IMGN853 (FORWARD I; NCT02631876). Methods: Pts were administered IMGN853 intravenously once every 3 weeks at 6 mg/kg using adjusted ideal body weight dosing. Responses were assessed according to RECIST 1.1 and adverse events (AEs) evaluated by CTCAE v4.0. Results: A total of 37 EOC pts treated as part of the three phase I expansion cohorts (pooled population; n = 113) met the FORWARD I enrollment criteria of moderate to high tumor FRα levels (≥ 50% of cells with ≥ 2+ FRα expression) and 1-3 prior lines of therapy. In this group of pts with platinum-resistant disease, confirmed objective tumor responses were observed in 17 individuals (1 complete response [CR] and 16 partial responses [PR]) for an overall response rate (ORR) of 46% (95% CI, 29.5, 63.1) and a median PFS of 6.7 months (95% CI, 4.1, 9.0). The safety profile of the pooled population was consistent with that previously reported (ASCO Annual Meeting, 2016) with the most common AEs being diarrhea, fatigue, nausea, and blurred vision; these were low grade and readily managed. Conclusions: IMGN853 continues to be characterized by favorable tolerability and encouraging activity in pts with platinum-resistant EOC. In particular, both the ORR (46%) and PFS (6.7 months) achieved in this group of pts are superior to outcomes typically seen with established single-agent chemotherapy within the setting of primary platinum resistance. Overall, these analyses provide continued, robust support for the patient eligibility strategy employed in the phase III evaluation of IMGN853. Clinical trial information: NCT01609556.

Safety findings from FORWARD II: A Phase 1b study evaluating the folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC) mirvetuximab soravtansine (IMGN853) in combination with bevacizumab, carboplatin, pegylated liposomal doxorubicin (PLD), or pembrolizumab in patients (pts) with ovarian cancer

5553

Background: FORWARD II is a phase 1b study of the FRα-targeting ADC, mirvetuximab soravtansine (IMGN853), in combination with bevacizumab (BEV), carboplatin, PLD, or pembrolizumab in adults with FRα-positive EOC, primary peritoneal, or fallopian tube tumors (NCT02606305). Methods: The escalation stage of this trial evaluated the safety and tolerability of IMGN853 as part of 4 combination regimens: IMGN853 + BEV; + carboplatin; + PLD; and + pembrolizumab. IMGN853 was administered in combination on Day 1 of a 21 (BEV or carboplatin) or 28-day cycle (PLD). Pembrolizumab escalation is continuing. The starting dose of IMGN853 was 5 mg/kg (adjusted ideal body weight, AIBW), one level lower than the recommended single agent phase 2 dose (RP2D; 6 mg/kg AIBW) defined in a first-in-human study (NCT01609556). Adverse events (AEs) were evaluated by CTCAE v4.0. Results: 46 pts enrolled in the first 3 cohorts. IMGN853 was escalated from 5 to 6 mg/kg. Carboplatin and PLD dosing were escalated from AUC4 to AUC5 and 30 to 40 mg/m2, respectively; BEV dosing remained constant at 15 mg/kg. Diarrhea, nausea, and fatigue were common across cohorts (all grades; 33-57%) and mostly low grade (i.e. ≤ 2), consistent with the IMGN853 safety profile from the earlier phase I monotherapy study. AEs of interest related to the combination agents were seen in each arm. For example, grade 1/2 proteinuria (36%) and grade 3 hypertension (21%) were only observed in the BEV combination. Thrombocytopenia (44%) and neutropenia (39%), grades 1-3, occurred most frequently in the carboplatin arm. Grade 3 anemia and vomiting (each 14%), as well as low grade (≤ 2) constipation (43%), were seen in the PLD cohort. Conclusions: The RP2D dose of IMGN853 was readily combined with the highest doses (as per protocol) of BEV, carboplatin, and PLD. The AE profiles for these combinations were manageable and as expected based on known profiles of each agent; importantly, no new safety signals were identified. Updated data from all 4 combination regimens will be presented. Clinical trial information: NCT02606305.

FORWARD I (GOG 3011): A randomized phase 3 study to evaluate the safety and efficacy of mirvetuximab soravtansine (IMGN853) versus chemotherapy in adults with folate receptor alpha (FRα)-positive, platinum-resistant epithelial ovarian cancer (EOC), primary peritoneal cancer, or primary fallopian tube cancer

TPS5607

Background: Elevated FRα expression is characteristic of a number of solid tumors, including EOC, thereby providing an attractive candidate for targeted therapeutic approaches. Mirvetuximab soravtansine is an antibody-drug conjugate (ADC), comprising a FRα-binding antibody linked to the tubulin-disrupting maytansinoid DM4, that has shown single agent clinical activity and a favorable safety profile in an ongoing, first-in-human phase 1 trial (NCT01609556). Methods: FORWARD I is a randomized phase 3 study designed to evaluate the efficacy of mirvetuximab soravtansine compared with that of standard-of-care chemotherapy in adult patients with platinum-resistant EOC, primary peritoneal cancer, or fallopian tube cancer. Confirmation of FRα positivity by immunohistochemistry (medium or high expression; ≥ 50% of cells with at least moderate staining intensity) and ≤ 3 prior lines of therapy are required for inclusion. A maximum of 333 patients are expected to be recruited. Patients will be randomized 2:1 to Arm 1 (intravenous mirvetuximab soravtansine at a dose of 6.0 mg/kg, calculated using adjusted ideal body weight, on Day 1 of a 21-day cycle) or Arm 2 (investigators’ choice chemotherapy: paclitaxel, pegylated liposomal doxorubicin, or topotecan). The primary efficacy endpoint is progression-free survival (PFS; by blinded independent central review) and secondary endpoints include objective response rate, quality of life, overall survival, safety and tolerability, and duration of response. The first patient was enrolled in January 2017. Clinical trial information: NCT02631876.

Phase 1 dose-escalation study of mirvetuximab soravtansine (IMGN853), a folate receptor α-targeting antibody-drug conjugate, in patients with solid tumors

BACKGROUND

Mirvetuximab soravtansine (IMGN853) is an antibody-drug conjugate that selectively targets folate receptor α (FRα). In this phase 1 dose-escalation study, the authors investigated IMGN853 in patients with FRα-positive solid tumors.

METHODS

Patients received IMGN853 on day 1 of a 21-day cycle (once every 3 weeks dosing), with cycles repeated until patients experienced dose-limiting toxicity or progression. Dose escalation commenced in single-patient cohorts for the first 4 planned dose levels and then followed a standard 3 + 3 scheme. The primary objectives were to determine the maximum tolerated dose and the recommended phase 2 dose. Secondary objectives were to determine safety and tolerability, to characterize the pharmacokinetic profile, and to describe preliminary clinical activity.

RESULTS

In total, 44 patients received treatment at doses escalating from 0.15 to 7.0 mg/kg. No meaningful drug accumulation was observed with the dosing regimen of once every 3 weeks. The most common treatment-related adverse events were fatigue, blurred vision, and diarrhea, the majority of which were grade 1 or 2. The dose-limiting toxicities observed were grade 3 hypophosphatemia (5.0 mg/kg) and grade 3 punctate keratitis (7.0 mg/kg). Two patients, both of whom were individuals with epithelial ovarian cancer, achieved confirmed tumor responses according to Response Evaluation Criteria in Solid Tumors 1.1, and each was a partial response.

CONCLUSIONS

IMGN853 demonstrated a manageable safety profile and encouraging preliminary clinical activity, particularly in patients with ovarian cancer. The results establish a recommended phase 2 dosing of 6.0 mg/kg (based on adjusted ideal body weight) once every 3 weeks. Cancer 2017. © 2017 American Cancer Society. Cancer 2017;123:3080-7. © 2017 American Cancer Society.

Safety and Activity of Mirvetuximab Soravtansine (IMGN853), a Folate Receptor Alpha-Targeting Antibody-Drug Conjugate, in Platinum-Resistant Ovarian, Fallopian Tube, or Primary Peritoneal Cancer: A Phase I Expansion Study

Purpose This phase I expansion cohort study evaluated the safety and clinical activity of mirvetuximab soravtansine (IMGN853), an antibody-drug conjugate consisting of a humanized anti-folate receptor alpha (FRα) monoclonal antibody linked to the tubulin-disrupting maytansinoid DM4, in a population of patients with FRα-positive and platinum-resistant ovarian cancer. Patients and Methods Patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer received IMGN853 at 6.0 mg/kg (adjusted ideal body weight) once every 3 weeks. Eligibility included a minimum requirement of FRα positivity by immunohistochemistry (≥ 25% of tumor cells with at least 2+ staining intensity). Adverse events, tumor response (via Response Evaluation Criteria in Solid Tumors [RECIST] version 1.1), and progression-free survival (PFS) were determined. Results Forty-six patients were enrolled. Adverse events were generally mild (≤ grade 2), with diarrhea (44%), blurred vision (41%), nausea (37%), and fatigue (30%) being the most commonly observed treatment-related toxicities. Grade 3 fatigue and hypotension were reported in two patients each (4%). For all evaluable patients, the confirmed objective response rate was 26%, including one complete and 11 partial responses, and the median PFS was 4.8 months. The median duration of response was 19.1 weeks. Notably, in the subset of patients who had received three or fewer prior lines of therapy (n = 23), an objective response rate of 39%, PFS of 6.7 months, and duration of response of 19.6 weeks were observed. Conclusion IMGN853 exhibited a manageable safety profile and was active in platinum-resistant ovarian cancer, with the strongest signals of efficacy observed in less heavily pretreated individuals. On the basis of these findings, the dose, schedule, and target population were identified for a phase III trial of IMGN853 monotherapy in patients with platinum-resistant disease.