Zolbetuximab plus mFOLFOX6 in patients with CLDN18.2-positive, HER2-negative, untreated, locally advanced unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma (SPOTLIGHT): a multicentre, randomised, double-blind, phase 3 trial

BACKGROUND

Zolbetuximab, a monoclonal antibody targeting claudin-18 isoform 2 (CLDN18.2), has shown efficacy in patients with CLDN18.2-positive, human epidermal growth factor receptor 2 (HER2)-negative, locally advanced unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma. We report the results of the SPOTLIGHT trial, which investigated the efficacy and safety of first-line zolbetuximab plus mFOLFOX6 (modified folinic acid [or levofolinate], fluorouracil, and oxaliplatin regimen) versus placebo plus mFOLFOX6 in patients with CLDN18.2-positive, HER2-negative, locally advanced unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma.

METHODS

SPOTLIGHT is a global, randomised, placebo-controlled, double-blind, phase 3 trial that enrolled patients from 215 centres in 20 countries. Eligible patients were aged 18 years or older with CLDN18.2-positive (defined as ≥75% of tumour cells showing moderate-to-strong membranous CLDN18 staining), HER2-negative (based on local or central evaluation), previously untreated, locally advanced unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma, with radiologically evaluable disease (measurable or non-measurable) according to Response Evaluation Criteria in Solid Tumors version 1.1; an Eastern Cooperative Oncology Group performance status score of 0 or 1; and adequate organ function. Patients were randomly assigned (1:1) via interactive response technology and stratified according to region, number of organs with metastases, and previous gastrectomy. Patients received zolbetuximab (800 mg/m2 loading dose followed by 600 mg/m2 every 3 weeks) plus mFOLFOX6 (every 2 weeks) or placebo plus mFOLFOX6. The primary endpoint was progression-free survival assessed by independent review committee in all randomly assigned patients. Safety was assessed in all treated patients. The study is registered with ClinicalTrials.gov, NCT03504397, and is closed to new participants.

FINDINGS

Between June 21, 2018, and April 1, 2022, 565 patients were randomly assigned to receive either zolbetuximab plus mFOLFOX6 (283 patients; the zolbetuximab group) or placebo plus mFOLFOX6 (282 patients; the placebo group). At least one dose of treatment was administered to 279 (99%) of 283 patients in the zolbetuximab group and 278 (99%) of 282 patients in the placebo group. In the zolbetuximab group, 176 (62%) patients were male and 107 (38%) were female. In the placebo group, 175 (62%) patients were male and 107 (38%) were female. The median follow-up duration for progression-free survival was 12·94 months in the zolbetuximab group versus 12·65 months in the placebo group. Zolbetuximab treatment showed a significant reduction in the risk of disease progression or death compared with placebo (hazard ratio [HR] 0·75, 95% CI 0·60-0·94; p=0·0066). The median progression-free survival was 10·61 months (95% CI 8·90-12·48) in the zolbetuximab group versus 8·67 months (8·21-10·28) in the placebo group. Zolbetuximab treatment also showed a significant reduction in the risk of death versus placebo (HR 0·75, 95% CI 0·60-0·94; p=0·0053). Treatment-emergent grade 3 or worse adverse events occurred in 242 (87%) of 279 patients in the zolbetuximab group versus 216 (78%) of 278 patients in the placebo group. The most common grade 3 or worse adverse events were nausea, vomiting, and decreased appetite. Treatment-related deaths occurred in five (2%) patients in the zolbetuximab group versus four (1%) patients in the placebo group. No new safety signals were identified.

INTERPRETATION

Targeting CLDN18.2 with zolbetuximab significantly prolonged progression-free survival and overall survival when combined with mFOLFOX6 versus placebo plus mFOLFOX6 in patients with CLDN18.2-positive, HER2-negative, locally advanced unresectable or metastatic gastric or gastro-oesophageal junction adenocarcinoma. Zolbetuximab plus mFOLFOX6 might represent a new first-line treatment in these patients.

FUNDING

Astellas Pharma, Inc.

Circulating Tumor DNA as a Predictive Biomarker for Clinical Outcomes With Margetuximab and Pembrolizumab in Pretreated HER2-Positive Gastric/ Gastroesophageal Adenocarcinoma

PURPOSE

To assess the ability of circulating tumor DNA (ctDNA)-based testing to identify patients with HER2 (encoded by ERBB2)-positive gastric/gastroesophageal adenocarcinoma (GEA) who progressed on or after trastuzumab-containing treatments were treated with combination therapy of anti-HER2 and anti-PD-1 agents.

METHODS

ctDNA analysis was performed retrospectively using plasma samples collected at study entry from 86 patients participating in the phase 1/2 CP-MGAH22-05 study (NCT02689284).

RESULTS

Objective response rate (ORR) was significantly higher in evaluable ERBB2 amplification-positive vs - negative patients based on ctDNA analysis at study entry (37% vs 6%, respectively; P = .00094). ORR was 23% across all patients who were evaluable for response. ERBB2 amplification was detected at study entry in 57% of patients (all HER2 positive at diagnosis), and detection was higher (88%) when HER2 status was determined by immunohistochemistry fewer than 6 months before study entry. ctDNA was detected in 98% (84/86) of patients tested at study entry. Codetected ERBB2-activating mutations were not associated with response.

CONCLUSIONS

Current ERBB2 status may be more effective than archival status at predicting clinical benefit from margetuximab plus pembrolizumab therapy. ctDNA testing for ERBB2 status prior to treatment will spare patients from repeat tissue biopsies, which may be reserved for reflex testing when ctDNA is not detected.

INTEGRATE II: randomised phase III controlled trials of regorafenib containing regimens versus standard of care in refractory Advanced Gastro-Oesophageal Cancer (AGOC): a study by the Australasian Gastro-Intestinal Trials Group (AGITG)

BACKGROUND

Advanced gastro-oesophageal cancer (AGOC) carries a poor prognosis. No standard of care treatment options are available after first and second-line therapies. Regorafenib is an oral multi-targeted tyrosine kinase inhibitor targeting angiogenic, stromal, and oncogenic receptor tyrosine kinases. Regorafenib 160 mg daily prolonged progression free survival compared to placebo (INTEGRATE, phase 2). Regorafenib 80 mg daily in combination with nivolumab 3 mg/kg showed promising objective response rates (REGONIVO).

METHODS/DESIGN

INTEGRATE II (INTEGRATE IIa and IIb) platform comprises two international phase III randomised controlled trials (RCT) with 2:1 randomisation in favor of experimental intervention. INTEGRATE IIa (double-blind) compares regorafenib 160 mg daily on days 1 to 21 of each 28-day cycle to placebo. INTEGRATE IIb (open label) compares REGONIVO, regorafenib 90 mg days 1 to 21 in combination with intravenous nivolumab 240 mg days 1 and 15 each 28-day cycle with investigator's choice of chemotherapy (control). Treatment continues until disease progression or intolerable adverse events as per protocol. Eligible participants include adults with AGOC who have failed two or more lines of treatment. Stratification is by location of tumour (INTEGRATE IIa only), geographic region, prior VEGF inhibitor and prior immunotherapy use (INTEGRATE IIb only). Primary endpoint is overall survival. Secondary endpoints are progression free survival, objective response rate, quality of life, and safety. Tertiary/correlative objectives include biomarker and pharmacokinetic evaluation.

DISCUSSION

INTEGRATE II provides a platform to evaluate the clinical utility of regorafenib alone, as well as regorafenib in combination with nivolumab in treatment of participants with refractory AGOC.

TRIAL REGISTRATION

INTEGRATE IIa prospectively registered 1 April 2016 Australia New Zealand Clinical Trial Registry: ACTRN12616000420448 (ClinicalTrials.gov NCT02773524). INTEGRATE IIb prospectively registered 10 May 2021 ClinicalTrials.gov: NCT04879368.

Zolbetuximab + mFOLFOX6 as first-line (1L) treatment for patients (pts) withclaudin-18.2+ (CLDN18.2+) / HER2− locally advanced (LA) unresectable or metastatic gastric or gastroesophageal junction (mG/GEJ) adenocarcinoma: Primary results from phase 3 SPOTLIGHT study

LBA292

Background: 1L treatment for pts with HER2−, mG/GEJ adenocarcinoma is typically chemotherapy and immunotherapy; an unmet need still exists. CLDN18.2 is expressed in normal gastric mucosa cells and retained in mG/GEJ tumor cells. In the FAST study, zolbetuximab, which targets CLDN18.2, prolonged survival of pts with LA unresectable or mG/GEJ adenocarcinoma when combined with chemotherapy. SPOTLIGHT (NCT03504397) is a phase 3 global, double-blind study comparing zolbetuximab + folinic acid, 5-FU, and oxaliplatin (mFOLFOX6) vs placebo + mFOLFOX6 as 1L treatment for pts with CLDN18.2+/ HER2−, LA unresectable or mG/GEJ adenocarcinoma. Methods: Previously untreated pts with CLDN18.2+ (moderate-to-strong membrane staining in ≥75% tumor cells by IHC)/HER2− LA unresectable or mG/GEJ adenocarcinoma were randomized 1:1 to zolbetuximab IV 800 mg/m2 (cycle [C] 1, day [D] 1) followed by 600 mg/m2 (C1D22, and every 3 weeks in later cycles) + mFOLFOX6 IV (D1, 15, 29) for four 42-day cycles vs placebo + mFOLFOX6; pts without PD continued for >4 cycles with zolbetuximab or placebo, + folinic acid and 5-FU at investigator’s discretion until PD or discontinuation criteria were met. The primary endpoint (EP) was PFS per RECIST v1.1 by IRC. Secondary EPs included OS, ORR, and safety. Differences in efficacy between treatment arms were tested by stratified log rank tests; OS was tested if PFS was significant. Results: Among 2735 pts screened, 565 pts were randomized 1:1 to zolbetuximab + mFOLFOX6 (N = 283) or placebo + mFOLFOX6 (N = 282). PFS was statistically significantly improved with zolbetuximab + mFOLFOX6 (median 10.61 vs 8.67 mo, HR 0.751, P=0.0066; Table). OS was also significantly improved (median 18.23 vs 15.54 mo, HR 0.750, P=0.0053, < 0.0135 as boundary; Table). ORR was similar between treatment arms. Most common TEAEs with zolbetuximab + mFOLFOX6 were nausea (82.4% vs 60.8% in zolbetuximab vs placebo arms), vomiting (67.4% vs 35.6%), and decreased appetite (47.0% vs 33.5%); the incidences of serious TEAEs were similar between both arms (44.8% vs 43.5%). Conclusions: Targeting CLDN18.2 with 1L zolbetuximab combined with mFOLFOX6 statistically significantly prolonged PFS and OS in pts with CLDN18.2+/ HER2−, LA unresectable or mG/GEJ adenocarcinoma. TEAEs were consistent with previous studies. Zolbetuximab + mFOLFOX6 may be a new option for these pts. Funding source: This study was funded by Astellas Pharma Inc. Medical writing support, conducted in accordance with Good Publication Practice (GPP 2022) and the International Committee of Medical Journal Editors (ICMJE) guidelines, was provided by Ann Ferguson, PhD, of Oxford PharmaGenesis Inc., Newtown, PA, USA, and funded by Astellas Pharma Inc. Clinical trial information: NCT03504397 . [Table: see text]

A phase 2 study of durvalumab plus DOS (docetaxel, oxaliplatin, S-1) neoadjuvant chemotherapy followed by surgery and adjuvant durvalumab plus S-1 chemotherapy in patients with resectable locally advanced gastric cancer: An interim efficacy report

408

Background: The phase 3 PRODIGY study showed that neoadjuvant docetaxel, oxaliplatin and S-1 (DOS) chemotherapy, as part of perioperative chemotherapy, was effective and tolerable in Asian patients with resectable locally advanced gastric cancer (LAGC). The current study aimed to evaluate the efficacy and safety of neoadjuvant durvalumab plus DOS, which was followed by surgery and adjuvant durvalumab plus S-1 chemotherapy in patients with resectable LAGC. Methods: In this single-center, open-label, phase II study, patients with locally advanced gastric or gastroesophageal junction cancer (i.e., cT2/3N+ or cT4Nany) were enrolled. In patients with proficient mismatch repair protein (pMMR) tumors (main arm), 3 cycles of neoadjuvant durvalumab plus DOS were administered every 3 weeks, which was followed by surgery and adjuvant S-1 plus durvalumab administered every 6 weeks for 12 months. The primary endpoints were the rate of pathologic complete regression (pCR) and the safety. For an exploratory purpose, patients with deficient mismatch repair protein tumors (exploratory arm) were treated with 3 cycles of neoadjuvant durvalumab and tremelimumab every 4 weeks followed by surgery and adjuvant durvalumab administered every 4 weeks for 12 months. At this interim analysis, we report the results of patients with pMMR. Results: As of SEP 2022, 40 subjects with pMMR were enrolled and received ≥ 1 dose of neoadjuvant treatment. Thirty-five subjects completed 3 cycles of neoadjuvant treatment, and 31 received surgery as of the data cut-off. Among 31 patients who received surgery, a pCR was confirmed in 9 (29.0%), meeting the primary efficacy endpoint (8 pCR out of 40) early. Among those who received 3 cycles of neoadjuvant treatment, 3 (8.6%) experienced the predefined unacceptable severe toxicities during the neoadjuvant treatment: febrile neutropenia (n=2) and G4 neutropenia persisted for ≥ 7 days (n=1). Conclusions: The current study met its primary efficacy endpoint and is expected to meet the primary safety endpoint (<20%). Neoadjuvant durvalumab plus DOS followed by surgery and adjuvant durvalumab plus S-1 chemotherapy deserves to be investigated in a phase 3 trial in Asian patients with LAGC. Clinical trial information: 04221555 .

Prognostic value of mismatch repair deficiency in patients receiving first-line fluoropyrimidine plus platinum chemotherapy for metastatic, recurrent, or locally advanced unresectable gastric cancer

461

Background: In localized gastric cancer (GC), deficient mismatch repair (dMMR) tumors reportedly have a favorable prognosis. However, a potentially detrimental effect of the dMMR status was suggested in patients treated with adjuvant chemotherapy. It remains unclear whether the mismatch repair (MMR) status can impact clinical outcomes in patients with metastatic GC (mGC) receiving palliative chemotherapy. We examined the impact of the MMR status on survival outcomes of patients with HER2-negative mGC receiving first-line fluoropyrimidine plus platinum (FP) chemotherapy. Methods: We reviewed patients with histologically confirmed metastatic, recurrent, or locally advanced unresectable adenocarcinoma of the stomach or gastroesophageal junction receiving first-line FP chemotherapy between January 2015 and August 2018 at Asan Medical Center, Korea. MMR status was correlated with clinical characteristics and survival outcomes for patients with available MMR immunohistochemistry results. Results: Of 895 patients, we analyzed 543 with available MMR protein expression results, and dMMR was detected in 4.4% (n=24). Patients with dMMR exhibited a significantly higher median age than those with proficient MMR (pMMR) (64 vs. 58 years, p=0.044). No signet ring cell carcinoma (SRCC) was detected among dMMR tumors, whereas SRCC was found in 17.5% of pMMR tumors. Based on our prognostic model (Koo DH et al, 2011), only 4.2% of patients with dMMR were classified as the poor-risk group (vs. 16.8% of patients with pMMR, p=0.097). No significant difference in progression-free survival (PFS) was noted between patients with dMMR and pMMR tumors (median, 5.6 vs. 5.8 months, p=0.266). Patients with dMMR tumors tended to have better overall survival than those with pMMR tumors; this difference was not statistically significant (median, 17.9 vs. 12.2 months, p=0.183). In the good-risk subgroup, patients with dMMR tumors had a significantly worse PFS than those with pMMR tumors (median, 5.6 vs. 9.2 months, p=0.009); multivariate analysis revealed that MMR status was an independent factor for poor PFS in this subgroup. Conclusions: Survival outcomes of dMMR mGC did not differ from pMMR in patients who received first-line FP chemotherapy. However, in the good-risk subgroup, patients with dMMR tumors had a significantly shorter PFS than those with pMMR, suggesting a potentially reduced efficacy of cytotoxic chemotherapy in these patients.

Zanidatamab + chemotherapy as first-line treatment for HER2-expressing metastatic gastroesophageal adenocarcinoma (mGEA)

347

Background: Zanidatamab (zani) is an anti-HER2 bispecific antibody against ECD4 and ECD2 with demonstrated activity and tolerability in a range of HER2-expressing cancers. This Phase (Ph) 2 study (NCT03929666) evaluates zani in combination with chemotherapy (chemo) as first-line treatment for patients (pts) with advanced HER2-expressing mGEA. Methods: Eligible pts for this ongoing, open-label study had not received any prior systemic therapy for mGEA. Pts received zani + physician’s choice of multi-agent chemo (mFOLFOX6, CAPOX, or FP). Antidiarrheal prophylaxis for cycle 1 was added after the first 25 pts were treated. Following demonstration of tolerability of the regimens in an initial safety cohort, the primary study objective was to evaluate antitumor activity. Results: Pts were enrolled between Aug 29, 2019 and Feb 18, 2022 with a data cutoff of July 28, 2022 (N=46 pts; zani + mFOLFOX6 [24], zani + CAPOX [20], or zani + FP [2]). Median age was 58 yrs; 85% male; 42 pts (91%) had HER2+ tumors (IHC 3+ or 2+ with ISH-positivity) based on central testing. Median duration of follow-up among all 46 pts was 21.5 months (mo) and 20 pts (43%) remain on treatment. In 38 response-evaluable pts with HER2+ tumors, confirmed objective response rate (cORR) was 79% (95% CI: 63-90%) and disease control rate was 92% (95% CI: 79-98%); 3 pts achieved complete response. Median duration of response (DOR) was 20.4 mo (95% CI: 6.8-not estimable [NE]), with 57% (17/30) pts having an ongoing response at data cut-off (1 pt has ongoing response >29 months). In all 42 pts with HER2+ tumors, median progression-free survival (PFS) was 12.5 mo (95% CI: 7.1-NE) and median overall survival (OS) was not yet reached. Survival rate at 18 mo was estimated to be 87.3%. The most common (≥25% pts) treatment-related (zani and/or chemo) adverse events (TRAE) in all pts were diarrhea, nausea, peripheral sensory neuropathy, decreased appetite, fatigue, vomiting, and hypokalemia. Diarrhea was the most common Gr3+ TRAE, lasting a median (interquartile range) of 3 (2-5) days, with the majority of events occurring in cycle 1; incidence of all Gr3+ events was 56% in 25 pts who did not receive prophylaxis and 14% in 21 pts who did. There were no treatment-related deaths. Conclusions: In pts with HER2+ mGEA, zani + chemo is a highly active treatment regimen with a manageable safety profile. This maturing data set demonstrates durable disease control with encouraging cORR, DOR, PFS and OS results. A global Ph 3 study (HERIZON-GEA-01; NCT05152147) evaluating zani in combination with physician’s choice of standard chemo with or without the PD-1 inhibitor, tislelizumab, for first-line treatment of advanced HER2+ mGEA is currently enrolling. Clinical trial information: NCT03929666 .

Phase II study of the combination of durvalumab, tremelimumab, and paclitaxel as second-line chemotherapy in biomarker-selected patients with metastatic gastric cancer

401

Background: Currently, ramucirumab plus paclitaxel is the standard second-line chemotherapy in metastatic gastric cancer (mGC), however, its efficacy is very limited. MSI, PD-L1 (CD274), and EBV have been suggested as predictive biomarkers for immune checkpoint inhibitors in mGC. This study was conducted to evaluate efficacy and safety of the combination of durvalumab, tremelimumab, and paclitaxel as a second-line chemotherapy in mGC with potential biomarkers for immune checkpoint inhibitors. Methods: The combination of durvalumab, tremelimumab, and paclitaxel consisted of 1500 mg of i.v. durvalumab on day 1, every 4 weeks for 13 cycles, 75 mg of i.v. tremelimumab on day 1 every 4 weeks for 4 cycles, and 60 mg/m2 of i.v. paclitaxel on days 1, 8, and 15, every 4 weeks until disease progression or unacceptable toxicities. Patients (pts) with MSI-high mGC, EBV-positive mGC, or mGC with CD274 amplification, mutations of mismatch repair or POL gene, or tumor mutation burden (TMB) >5/Mb were included in second-line setting. Results: Forty-eight pts were enrolled. Overall response rate (ORR) was 52.1% with complete response in 4 (8.3%) pts, partial response in 21 (43.8%), stable disease in 14 (29.2%), and progressive disease in 8 (16.7%), and with response not evaluable in 1 (2.0%). With a median follow-up of 18.0 months (range, 7.1-39.4), the median progression-free survival (PFS) and overall survival (OS) were 5.3 months (95% CI, 3.7-6.9) and 13.1 months (95% CI, 5.2-21.0 ), respectively. Compared to mGC with other genetic alterations (n=25), mGC with TMB >20/Mb or MSI-high mGC (n=23) tended to have a higher ORR (56.5% vs 48%), and a prolonged PFS (median 7.2 vs 4.5 months; 44.0 vs 20.8% at 1 year). The combination chemotherapy was generally well tolerable; treatment-related grade 3 or 4 adverse events with frequency >5% included only neutropenia (10.4%) and anemia (8.3%), and there was no treatment-related death. Conclusions: The combination chemotherapy of durvalumab, tremelimumab, and paclitaxel showed encouraging efficacy, especially in mGC with TMB >20/Mb or MSI-high mGC, as a second-line chemotherapy with manageable toxicities in biomarker-selected mGC. Clinical trial information: NCT03751761 .

DNA mismatch repair deficiency and outcomes of patients with resectable locally advanced gastric cancer treated with preoperative docetaxel, oxaliplatin, and S-1 plus surgery and postoperative S-1 or surgery and postoperative S-1: A sub-analysis of the phase 3 PRODIGY trial

431

Background: Benefit of perioperative or postoperative chemotherapy for resectable locally advanced gastric cancer (LAGC) with DNA mismatch repair (MMR) deficiency is controversial due to concerns about the potential detrimental effect of perioperative chemotherapy. In this sub-analysis of the phase 3 PRODIGY trial, we evaluated the association between the MMR status and outcomes of resectable LAGC treated with perioperative or postoperative chemotherapy. Methods: Among 249 patients with resectable LAGC enrolled in the PRODIGY trial treated with either perioperative chemotherapy (preoperative docetaxel, oxaliplatin, and S-1 [DOS] followed by surgery and postoperative S-1; CSC arm) or surgery and postoperative S-1 (SC arm) at Asan Medical Center, those in the full analysis set with available tissue for MMR status assessment by immunohistochemistry were included in this study. Progression-free survival (PFS) was compared according to the MMR status and treatment arm. In the CSC arm, the pathologic complete response (pCR) rate was compared according to the MMR status. Results: A total of 231 patients (CSC arm, n = 108; SC arm, n = 123) were included in the study (median age, 58 years [range, 27–75]). Twenty-one patients (CSC arm, n = 8 [7.4%]; SC arm, n = 13 [10.6%]) had deficient MMR (D-MMR) tumors while the rest had proficient MMR (P-MMR) tumors. There was no significant difference in the baseline characteristics including the clinical stage according to the MMR status. Among patients with P-MMR tumors, PFS tended to be superior in the CSC arm than in the SC arm (hazard ratio [HR] 0.67 [95% confidence interval (CI) 0.44–1.03]; log-rank P = 0.07). Among patients with D-MMR tumors, the PFS of the CSC arm was not inferior to that of the SC arm (HR 0.50 [95% CI 0.10–2.60]; log-rank P = 0.41). In the CSC arm, the pCR rate was 5.0% (5/100) and 12.5% (1/8) in patients with P-MMR and D-MMR tumors, respectively. Conclusions: In this sub-analysis of the PRODIGY trial, the PFS of the CSC arm was not inferior to that of the SC arm among patients with D-MMR LAGC. Among patients who received preoperative DOS, the pCR rate was not lower in patients with D-MMR tumors compared with those with P-MMR tumors. Perioperative chemotherapy consisting of preoperative DOS followed by surgery and postoperative S-1 may be recommended for patients with LAGC regardless of the MMR status.

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]

Pertuzumab, trastuzumab, and chemotherapy in HER2-positive gastric/gastroesophageal junction cancer: end-of-study analysis of the JACOB phase III randomized clinical trial

BACKGROUND

Dual-targeted anti-HER2 therapy significantly improves outcomes in HER2-positive breast cancer and could be beneficial in other HER2-positive cancers. JACOB's end-of study analyses aimed to evaluate the long-term efficacy and safety of pertuzumab plus trastuzumab and chemotherapy for previously untreated HER2-positive metastatic gastric or gastroesophageal junction cancer.

METHODS

Eligible patients were randomized 1:1 to pertuzumab/placebo plus trastuzumab and chemotherapy every 3 weeks.

PRIMARY ENDPOINT

overall survival (OS). Secondary endpoints included progression-free survival (PFS), objective response rate (ORR), duration of response (DoR), and safety.

RESULTS

The intention-to-treat population comprised 388 patients in the pertuzumab arm and 392 in the placebo arm. The safety population comprised 385 and 388 patients, respectively. Median follow-up was ≥ 44.4 months. Median OS was increased by 3.9 months (hazard ratio 0.85 [95% confidence intervals, 0.72-0.99]) and median PFS by 1.3 months (hazard ratio 0.73 [95% confidence intervals, 0.62-0.85]) in the pertuzumab vs. the placebo arm. ORR was numerically higher (57.0% vs. 48.6%) and median DoR 1.8 months longer with pertuzumab treatment. There was a trend for more favorable hazard ratios in certain subgroups related to HER2 amplification/overexpression. Safety was comparable between arms, except for serious and grade 3-5 adverse events, and any-grade diarrhea, which were more frequent with pertuzumab.

CONCLUSIONS

JACOB did not meet its primary endpoint. Nonetheless, the study continues to demonstrate some, albeit limited, evidence of treatment activity and an acceptable safety profile for pertuzumab plus trastuzumab and chemotherapy in previously untreated HER2-positive metastatic gastric or gastroesophageal junction cancer after long-term follow-up. Trial registration NCT01774786; https://clinicaltrials.gov/ct2/show/NCT01774786 .

Randomized phase II study of capecitabine plus cisplatin with or without sorafenib in patients with metastatic gastric cancer (STARGATE)

BACKGROUND

In this randomized phase II study, we evaluated the efficacy and safety of sorafenib in combination with capecitabine and cisplatin (XP) as first-line chemotherapy in advanced gastric cancer.

PATIENTS AND METHODS

Patients with metastatic gastric or gastroesophageal junction adenocarcinoma were randomized (1:1) to receive either sorafenib plus XP (S + XP) or XP alone. In cases of disease progression in the XP arm, crossover to sorafenib alone was allowed. The primary endpoint was progression-free survival (PFS). The secondary endpoints included overall survival (OS), response rates, safety profiles, and biomarkers, and the response rates and PFS with secondline sorafenib alone after progression in the XP arm.

RESULTS

Between Jan 2011 and Feb 2013, a total of 195 patients were accrued (97 in the S + XP arm and 98 in the XP alone arm). The overall response rate was 54% with S + XP, and 52% with XP alone (p = 0.83). With a median follow-up of 12.6 months (range, 0.1-29.2), the median PFS assessed by independent review was 5.6 months in the S + XP arm and 5.3 months in the XP arm (hazard ratio [HR] 0.92, 95% confidence interval [CI] 0.67-1.27, p = 0.61). Overall survival was not different between the two arms (median 11.7 vs. 10.8 months; HR 0.93, 95% CI 0.65-1.31, p = 0.66). Frequencies of grade 3/4 toxicities were similar between the S + XP and XP alone arms, except for neutropenia (21% vs. 37%), anorexia (0% vs. 5%), and hand-foot skin reaction (7% vs. 1%). Among 51 patients who crossed over to sorafenib alone after disease progression in the XP arm, there was no objective response and their median PFS was 1.3 months (95% CI, 1.2-1.7).

CONCLUSION

The addition of sorafenib to XP chemotherapy was safe but not more effective than XP alone for first-line treatment of metastatic gastric cancer.

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.

Association of PD-L1 Expression and Other Variables With Benefit From Immune Checkpoint Inhibition in Advanced Gastroesophageal Cancer: Systematic Review and Meta-analysis of 17 Phase 3 Randomized Clinical Trials

Importance

Approval by the US Food and Drug Administration of immune checkpoint inhibition (ICI) for advanced gastroesophageal cancer (aGEC) irrespective of PD-L1 status has generated controversy. Exploratory analyses from individual trials indicate a lack of meaningful benefit from ICI in patients with absent or low PD-L1 expression; however, analysis of a single variable while ignoring others may not consider the instability inherent in exploratory analyses.

Objective

To systematically examine the predictive value of tissue-based PD-L1 status compared with that of other variables for ICI benefit in aGEC to assess its stability.

Data Sources

MEDLINE, Embase, Scopus, Web of Science, Cochrane Central Register (2000-2022).

Study Selection, Data Extraction, and Synthesis

Randomized clinical trials (RCTs) were included of adults with aGEC (adenocarcinoma [AC] or squamous cell carcinoma [SCC]) randomized to anti-PD-1 or PD-L1-containing treatment vs standard of care (SOC). Study screening, data abstraction, and bias assessment were completed independently by 2 reviewers. Of 5752 records screened, 26 were assessed for eligibility; 17 trials were included in the analysis.

Main Outcomes and Measures

The prespecified primary end point was overall survival. The mean hazard ratio (HR) for ICI vs SOC was calculated (random-effects model). Predictive values were quantified by calculating the ratio of mean HRs between 2 levels of each variable.

Results

In all, 17 RCTs (9 first line, 8 after first line) at low risk of bias and 14 predictive variables were included, totaling 11 166 participants (5067 with SCC, 6099 with ACC; 77.6% were male and 22.4% were female; 59.5% of patients were younger than 65 years, 40.5% were 65 years or older). Among patients with SCCs, PD-L1 tumor proportion score (TPS) was the strongest predictor of ICI benefit (HR, 0.60 [95% CI, 0.53-0.68] for high TPS; and HR, 0.84 [95% CI, 0.75-0.95] for low TPS), yielding a predictive value of 41.0% favoring high TPS (vs ≤16.0% for other variables). Among patients with AC, PD-L1 combined positive score (CPS) was the strongest predictor (after microsatellite instability high status) of ICI benefit (HR, 0.73 [95% CI, 0.66-0.81] for high CPS; and HR, 0.95 [95% CI, 0.84-1.07] for low CPS), yielding a predictive value of 29.4% favoring CPS-high (vs ≤12.9% for other variables). Head-to-head analyses of trials containing both levels of a variable and/or having similar design generally yielded consistent results.

Conclusions and Relevance

Tissue-based PD-L1 expression, more than any variable other than microsatellite instability-high, identified varying degrees of benefit from ICI-containing therapy vs SOC among patients with aGEC in 17 RCTs.

Tremelimumab plus Durvalumab in Unresectable Hepatocellular Carcinoma

BACKGROUND: A single, high priming dose of tremelimumab (anti-cytotoxic T lymphocyte–associated antigen 4) plus durvalumab (anti–programmed cell death ligand-1), an infusion regimen termed STRIDE (Single Tremelimumab Regular Interval Durvalumab), showed encouraging clinical activity and safety in a phase 2 trial of unresectable hepatocellular carcinoma. METHODS: In this global, open-label, phase 3 trial, the majority of the patients we enrolled with unresectable hepatocellular carcinoma and no previous systemic treatment were randomly assigned to receive one of three regimens: tremelimumab (300 mg, one dose) plus durvalumab (1500 mg every 4 weeks; STRIDE), durvalumab (1500 mg every 4 weeks), or sorafenib (400 mg twice daily). The primary objective was overall survival for STRIDE versus sorafenib. Noninferiority for overall survival for durvalumab versus sorafenib was a secondary objective. RESULTS: In total, 1171 patients were randomly assigned to STRIDE (n=393), durvalumab (n=389), or sorafenib (n=389). The median overall survival was 16.43 months (95% confidence interval [CI], 14.16 to 19.58) with STRIDE, 16.56 months (95% CI, 14.06 to 19.12) with durvalumab, and 13.77 months (95% CI, 12.25 to 16.13) with sorafenib. Overall survival at 36 months was 30.7%, 24.7%, and 20.2%, respectively. The overall survival hazard ratio for STRIDE versus sorafenib was 0.78 (96.02% CI, 0.65 to 0.93; P=0.0035). Overall survival with durvalumab monotherapy was noninferior to sorafenib (hazard ratio, 0.86; 95.67% CI, 0.73 to 1.03; noninferiority margin, 1.08). Median progression-free survival was not significantly different among all three groups. Grade 3/4 treatment-emergent adverse events occurred for 50.5% of patients with STRIDE, 37.1% with durvalumab, and 52.4% with sorafenib. CONCLUSIONS: STRIDE significantly improved overall survival versus sorafenib. Durvalumab monotherapy was noninferior to sorafenib for patients with unresectable hepatocellular carcinoma. (Funded by AstraZeneca; ClinicalTrials.gov number, NCT03298451.)

Association between HER2 heterogeneity and clinical outcomes of HER2-positive gastric cancer patients treated with trastuzumab

BACKGROUND

The GASTHER1 study showed that re-evaluation of HER2 status rescued 8% of HER2-positive gastric cancer (GC) patients with initially HER2-negative GC. Since rescued HER2 positivity represents HER2 heterogeneity, we aimed to investigate this in a larger cohort with longer follow-up duration.

METHODS

Data of 153 HER2-positive advanced GC patients who received first-line trastuzumab-based chemotherapy were analyzed. Repeat endoscopic biopsy was performed in patients with initially HER2-negative GC. Survival outcomes were analyzed according to the immunohistochemistry (IHC) score (IHC 2+ /in situ hybridization [ISH] + vs IHC 3+), HER2 status (initially vs rescued HER2 positive), and H-score.

RESULTS

IHC 2+ /ISH + patients showed worse progression-free survival (PFS) and overall survival (OS) than those with IHC 3+ (p < 0.05). Rescued HER2-positive patients showed worse PFS and OS than initially HER2-positive patients (p < 0.05). Although survival outcomes were comparable according to HER2 status in IHC 2+ /ISH + patients, initially HER2-positive patients showed more favorable PFS and OS than rescued HER2-positive patients (p < 0.05) among those with IHC 3+ . Among the subgroups determined by HER2 status and IHC score, the initially IHC 3+ subgroup had the highest H-score. The low H-score group (H-score ≤ 210) had significantly worse survival outcomes than the high H-score group (H-score > 210) (p < 0.05). An H-score of ≤ 210 was independently associated with shorter OS (HR = 1.54, 95% CI 1.02-2.31, p = 0.04).

CONCLUSIONS

Rescued HER2-positive patients showed worse clinical outcomes than initially HER2-positive patients, especially those with IHC 3+ . This finding highlights the impact of HER2 heterogeneity, which can be quantified indirectly as an H-score.

Abstract CT015: Safety and efficacy of TTX-030, an anti-CD39 antibody, in combination with chemoimmunotherapy for the first line treatment of locally advanced or metastatic gastric/GEJ cancer

Background: The ecto-ATPase CD39 is the rate-limiting enzyme in the adenosine pathway that plays an important immune regulatory role. Preclinically, inhibition of CD39 by TTX-030, a first-in-class fully human anti-CD39 antibody, reversed immunosuppression by maintaining high levels of immune-stimulatory extracellular ATP while reducing suppressive adenosine. The addition of nivolumab to chemotherapy has recently become the standard of care of 1st-line (1L) treatment of locally advanced or metastatic (LA/M) gastric cancer but further improvements are needed.

Methods: An expansion cohort of Study TTX-030-002 (ongoing, US and South Korea) is evaluating the safety and efficacy of the combination of TTX-030, budigalimab (anti-PD-1) and FOLFOX for the 1L treatment of patients (pts) with LA/M HER2− gastric/GEJ adenocarcinoma. The primary objective was to assess safety and tolerability. Secondary endpoints included ORR by RECIST/iRECIST, and PFS. Correlative studies included the analysis of intratumoral expression of CD39 and PD-L1.

Results: Forty-four pts were enrolled with the median age [range] of 61 [30−81] years, 41% were female, and 57% were Asian. Pts had an ECOG of 0 (39%) or 1 (61%), 70% had gastric adenocarcinoma, 30% had GEJ adenocarcinoma. As of the safety data cutoff (Nov 19, 2021), 39 pts (89%) experienced at least 1 treatment-emergent AE (any Grade, regardless of relatedness). Twenty-one pts (48%) experienced at least 1 AE considered related to TTX-030 (any Grade); five (11%) experienced a Grade 3/4 AE considered related to TTX-030. There were no Grade 5 TEAEs. Eleven pts (25%) had experienced SAEs; none were considered related to TTX-030. The most common AEs by preferred term (any Grade, regardless of relatedness) in ≥10 pts were nausea (52%), neutrophil count decreased (39%), decreased appetite (30%), diarrhea (25%), and fatigue (23%). The most common Grade ≥3 AEs (regardless of relatedness) in ≥2 pts were neutrophil count decreased (27%), febrile neutropenia (5%), hypokalemia (5%). As of the efficacy data cutoff (Dec 2, 2021), the median time [range] on study was 139 [8−375] days. Among 38 efficacy evaluable pts, 23 pts experienced PR or better as best response (PR: n=21; CR: n=2; ORR=61%), 12 experienced SD, and 3 had PD. Thirty-six of the 38 efficacy-evaluable patients had known PD-L1 Combined Positive Score (CPS); response rates were 4/10 (CPS &lt;1), 8/10 (CPS ≥1 and &lt;5), and 11/16 (CPS ≥ 5).

Conclusions: Preliminary results indicate that the combination of TTX-030, budigalimab and FOLFOX exhibited promising efficacy as 1L treatment of LA/M gastric/GEJ cancer regardless of CPS status and has a manageable safety profile without evidence of excessive toxicities. To our knowledge, this represents the first report of an anti-CD39 antibody in combination with chemo-immunotherapy in gastric cancer. Updated clinical and biomarker data will be included in the final presentation.

Citation Format: Zev Wainberg, Yoon-Koo Kang, Keun-Wook Lee, Seung Tae Kim, Joseph Chao, Daniel Catenacci, Sung Yong Oh, Heloisa P. Soares, J. Eva Selfridge, Yongjun Cha, Roland T. Skeel, Hyung-Don Kim, Anh Tran, Achim Moesta, Tracy Dela Cruz, Anil Singhal, Thomas M. Jahn, Farshid Dayyani. Safety and efficacy of TTX-030, an anti-CD39 antibody, in combination with chemoimmunotherapy for the first line treatment of locally advanced or metastatic gastric/GEJ cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT015.

Clinical outcomes and prognostic factors for patients with high-risk gastrointestinal stromal tumors treated with 3-year adjuvant imatinib

Three years of adjuvant imatinib is the current standard for patients with high-risk gastrointestinal stromal tumors (GIST). We aimed to investigate the safety and efficacy profiles of 3-year imatinib, focusing on the prognostic value of various factors. In this registry-based study, 222 patients with high-risk GIST who underwent surgical resection followed by 3 years of adjuvant imatinib between 2010 and 2018 were included. The imatinib dose was reduced in 39 (17.6%), and 13 (5.9%) discontinued imatinib due to toxicity. With a median follow-up duration of 65.7 months, 5-year recurrence-free survival (RFS) and overall survival (OS) were 73.2% and 93.9%, respectively. Tumor rupture, tumor size of > 10 cm, mitotic index of > 10/50 high power fields (HPF) were independent factors for short RFS. Patient subgroups stratified by the risk factors showed distinct RFS (P < 0.001): patients without the above risk factors or those with only a tumor size of >10 cm showed favorable RFS (5-year RFS 83.8% and 92.3%, respectively), whereas those with tumor rupture or those with tumor size of > 10 cm and mitotic index of >10/50 HPF showed prominently poor RFS (5-year RFS of 54.8% and 47.9%, respectively). Three years of adjuvant imatinib treatment was generally tolerable and effective, which were consistent with the clinical outcomes of previous reports. The presence of tumor rupture, large tumor, and high mitotic count was independently associated with poor RFS. Based on these risk factors, different management strategies, such as different durations of adjuvant imatinib, deserve further investigation. This article is protected by copyright. All rights reserved.

A first-in-human phase 1/2 study of FGF401 and combination of FGF401 with spartalizumab in patients with hepatocellular carcinoma or biomarker-selected solid tumors

BACKGROUND

Deregulation of FGF19-FGFR4 signaling is found in several cancers, including hepatocellular carcinoma (HCC), nominating it for therapeutic targeting. FGF401 is a potent, selective FGFR4 inhibitor with antitumor activity in preclinical models. This study was designed to determine the recommended phase 2 dose (RP2D), characterize PK/PD, and evaluate the safety and efficacy of FGF401 alone and combined with the anti-PD-1 antibody, spartalizumab.

METHODS

Patients with HCC or other FGFR4/KLB expressing tumors were enrolled. Dose-escalation was guided by a Bayesian model. Phase 2 dose-expansion enrolled patients with HCC from Asian countries (group1), non-Asian countries (group2), and patients with other solid tumors expressing FGFR4 and KLB (group3). FGF401 and spartalizumab combination was evaluated in patients with HCC.

RESULTS

Seventy-four patients were treated in the phase I with single-agent FGF401 at 50 to 150 mg. FGF401 displayed favorable PK characteristics and no food effect when dosed with low-fat meals. The RP2D was established as 120 mg qd. Six of 70 patients experienced grade 3 dose-limiting toxicities: increase in transaminases (n = 4) or blood bilirubin (n = 2). In phase 2, 30 patients in group 1, 36 in group 2, and 20 in group 3 received FGF401. In total, 8 patients experienced objective responses (1 CR, 7 PR; 4 each in phase I and phase II, respectively). Frequent adverse events (AEs) were diarrhea (73.8%), increased AST (47.5%), and ALT (43.8%). Increase in levels of C4, total bile acid, and circulating FGF19, confirmed effective FGFR4 inhibition. Twelve patients received FGF401 plus spartalizumab. RP2D was established as FGF401 120 mg qd and spartalizumab 300 mg Q3W; 2 patients reported PR.

CONCLUSIONS

At biologically active doses, FGF401 alone or combined with spartalizumab was safe in patients with FGFR4/KLB-positive tumors including HCC. Preliminary clinical efficacy was observed. Further clinical evaluation of FGF401 using a refined biomarker strategy is warranted.

TRIAL REGISTRATION

NCT02325739 .

Trial in progress: Phase 1b/3 study of bemarituzumab + mFOLFOX6 + nivolumab versus mFOLFOX6 + nivolumab in previously untreated advanced gastric and gastroesophageal junction (GEJ) cancer with FGFR2b overexpression (FORTITUDE-102)

TPS4165

Background: Fibroblast growth factor receptor 2b (FGFR2b) is overexpressed in approximately 30% of non-human epidermal growth factor receptor 2 (non-HER2) positive gastric cancer (Wainberg, 2021). Bemarituzumab is a first-in-class monoclonal antibody that specifically blocks FGFR2b, inhibiting downstream tumor proliferation and enhancing antibody dependent cellular cytotoxicity (Catenacci, 2020; Xiang, 2021). In the phase 2 FIGHT study (Wainberg, 2021; Catenacci, 2021), progression-free survival (PFS) was improved (HR, 0.68; 95% CI, 0.44-1.04; p = 0.07) and a 5.7 month longer median overall survival (OS) was observed (19.2 months vs 13.5 months; HR, 0.60; 95% CI, 0.38-0.94) with bemarituzumab + mFOLFOX6 vs placebo + mFOLFOX6. Preclinical studies indicate that bemarituzumab modulates the tumor microenvironment to sensitize tumors to anti-PD1 monoclonal antibodies (Powers, 2016; Xiang, 2021) providing rationale for combination with nivolumab. Methods: FORTITUDE-102 (NCT05111626) is a phase 1b/3 study in patients (pts) with unresectable locally advanced or metastatic gastric or GEJ adenocarcinoma not amenable to curative therapy. Part 1 is an open-label safety lead-in; Part 2 is a double-blind, placebo-controlled study to evaluate efficacy and safety. Approximately 702 pts ≥18 years will be enrolled (Part 1, ̃20; Part 2, ̃682). Key eligibility criteria include Eastern Cooperative Oncology Group performance status 0-1, evaluable disease per RECIST v1.1, adequate hematologic and organ function, and no contraindication to receive mFOLFOX6 chemotherapy or nivolumab; for part 2, IHC-confirmed FGFR2b overexpression by central testing is required and no prior treatment for metastatic or unresectable disease allowed except 1 dose of mFOLFOX6 ± nivolumab. Key exclusion criteria include positive HER2 status and untreated or symptomatic CNS metastasis and leptomeningeal disease. Pts on bemarituzumab will receive 15 mg/kg every 2 weeks (Q2W) with an additional 7.5 mg/kg dose on cycle 1 day 8. mFOLFOX6 + nivolumab will be at a fixed dose Q2W. The dose-limiting toxicity (DLT) period is 28 days; observed safety data will influence additional enrollment to Part 1, de-escalation of bemarituzumab, or the recommended phase 3 dose (RP3D). For Part 1, primary endpoints are DLTs and adverse events; secondary endpoints include OS, PFS, and objective response (OR). For Part 2, pts will be randomized 1:1 to mFOLFOX6 + nivolumab Q2W plus either bemarituzumab at RP3D or placebo. Primary endpoint for Part 2 is OS; secondary endpoints include PFS, OR, and safety. The concurrent phase 3 FORTITUDE-101 study (NCT05052801) will evaluate bemarituzumab + mFOLFOX6 vs placebo + mFOLFOX6. Clinical trial information: NCT05111626.

A randomized phase 2 study of continuous or intermittent dosing schedule of imatinib re-challenge in patients with tyrosine kinase inhibitor-refractory gastrointestinal stromal tumors

11538

Background: Resumption of imatinib is one of the available therapeutic options for patients with gastrointestinal stromal tumors (GIST) refractory to tyrosine kinase inhibitors (TKIs). Intermittent dosing of imatinib was suggested to delay outgrow of the imatinib-resistant clones in a preclinical study. Methods: A randomized phase 2 study was performed to evaluate the efficacy and safety of continuous or intermittent schedule of imatinib in GIST patients whose disease had progressed to at least imatinib and sunitinib. Patients were randomly assigned (1:1) to the intermittent dosing group that received 400mg daily imatinib based on a 1 week-on and 1 week-off schedule or the continuous dosing group that received imatinib 400mg daily without drug holiday. Disease control rate (DCR) rate at 12 weeks was the primary endpoint. Plasma samples were collected for circulating tumor DNA analysis at baseline, at 3 months of continuous or intermittent imatinib treatment and at the time of progressive disease. Results: Fifty patients received at least one dose of imatinib and were included in the full analysis set. Most patients (n = 46) had received prior regorafenib. DCR rate at 12 weeks was 34.8% and 43.5% in the continuous and intermittent groups, respectively. Median progression-free survival was 1.68 months and 1.57 months in the continuous and intermittent groups, respectively. The frequency of any grade anorexia, dysphagia, diarrhea, decreased neutrophil was lower in the intermittent group, whereas that of abdominal pain was higher in the intermittent group. Two patients in the continuous imatinib group underwent dose modification, and there was no patient who discontinued the study treatment because of adverse events related to study treatment. Conclusions: We confirmed that imatinib re-challenge was effective in TKI-refractory GIST patients. Intermittent dosing schedule may also be a clinically feasible treatment option for imatinib resumption in TKI-refractory GIST patients. Clinical trial information: NCT02712112.

Circulating tumor DNA (ctDNA) analyses of the phase III VOYAGER trial: KIT mutational landscape and outcomes in patients with advanced gastrointestinal stromal tumor (GIST)

101

Background: The genotype of primary mutations predicts imatinib response in untreated metastatic GIST. However, the sequence of salvage treatments in metastatic GIST is based solely on the chronological order of registration trials. ctDNA sequencing offers a powerful diagnostic tool to detect resistance mutations in GIST but has not been shown to correlate with outcomes in clinical trials of pretreated patients (pts). We analyzed ctDNA samples collected at baseline in the phase III VOYAGER trial (NCT03465722) to describe the landscape of KIT alterations and its association with outcomes of pts treated with avapritinib or regorafenib. Methods: In VOYAGER, 476 pts with advanced KIT-mutant GIST were randomly assigned to avapritinib (240 pts) or regorafenib (236 pts) in 3rd-4th line. Baseline plasma was collected and ctDNA analyzed with the Guardant 360 (G360), 74-gene panel. KIT molecular subgroups were determined and correlated with outcomes. PDGFRA-mutant GISTs were excluded from outcomes analysis. Results: Baseline ctDNA analysis was performed in 386/476 pts (81%). ctDNA was detected in 333 pts (86%), with 250 and 18 pts showing at least one KIT (75%) or PDGFRA (5%) variant, respectively. KIT primary mutations were detected in 71% pts (exon 11, 56%; exon 9, 14%; exon 13, 1%) and KIT secondary mutations in 55% of pts. Activation loop (AL, exons 17 and 18) was more commonly affected (44%) than the ATP-binding pocket (ABP, exons 13 and 14; 23%). Among KIT-mutant tumors, multiple KIT mutations were commonly detected within individual tumors (mean, 2.56; range, 1-14). Notably, 17% of pts had > 3 mutations (mean, 6.07; range, 4 to 14). Median PFS and OS were shorter for patients whose ctDNA was positive for V654A or T670I (ABP hot spots) when treated with avapritinib vs. regorafenib: mPFS, 1.9 mo vs. 7.4 mo; log-rank p <.001; mOS, 8.3 mo vs. 11.7 mo; log rank p =.0651. mPFS was shorter for patients with ctDNA positive for KIT exon 17 mutation if concurrently KIT V654A/T670I was absent when treated with avapritinib, with no difference in OS: mPFS, 4.7 mo vs. 6.7 mo; log-rank p =.03; mOS, 19.2 mo vs. NR; log-rank p =.628. mPFS on avapritinib was longer when ABP mutations were absent when compared to those with ABP present (5.6 vs. 1.9 mo; log-rank p <.001). There were no differences considering AL mutations vs. no AL mutations (3.8 vs. 3.9 mo; log-rank p =.622) when treated with avapritinib. Regorafenib showed similar activity regardless of KIT mutational status and the location of KIT mutation. Conclusions: Hybrid capture-based plasma sequencing detects ctDNA in the majority of patients with advanced TKI-resistant GIST, including heterogeneity of KIT mutations. This study is the first to show that ctDNA sequencing correlates with outcomes in pretreated GIST. Identification of ABP (exon13/14) KIT mutations negatively correlates with avapritinib activity.

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.

First-in-human study of SRF388, a first-in-class IL-27 targeting antibody, as monotherapy and in combination with pembrolizumab in patients with advanced solid tumors

2501

Background: The immunoregulatory cytokine IL-27 upregulates inhibitory immune checkpoint receptors (eg, PD-L1, TIGIT) and downregulates proinflammatory cytokines (eg, IFNγ, TNFα). SRF388 is a fully human IgG1 blocking antibody to IL-27 with potential to promote immune activation in the tumor microenvironment. A phase 1 study was conducted to establish the preliminary safety of SRF388 and to identify recommended phase 2 doses (RP2D) suitable for monotherapy and combination expansions (NCT04374877). Methods: The dose-escalation study (accelerated single patient followed by standard 3+3) enrolled patients (pts) with advanced treatment-refractory solid tumors. Upon RP2D selection, monotherapy and combination expansions opened for treatment-refractory clear cell renal cell cancer (ccRCC), hepatocellular cancer (HCC), and non-small cell lung cancer. SRF388 was administered IV every 4 weeks (wks) as monotherapy and every 3 wks with pembrolizumab. Tumor response was assessed by RECIST1.1. Results: The monotherapy dose-escalation enrolled 29 pts with doses ranging from 0.003 to 20 mg/kg. Median age was 64 years. Most pts were female (62%) with ECOG PS of 1 (72%). Approximately 80% had prior PD-(L)1 blockade, and 48% had ≥4 prior therapies. Treatment-related adverse events (TRAEs) occurred in 21%, and all were low grade. Fatigue was the only TRAE reported in ≥10% (n = 3). No dose-limiting toxicities (DLTs) or Grade ≥3 TRAEs were observed. Median time on study was 9 wks (range 0–59). One patient with highly treatment-refractory NSCLC experienced a confirmed partial response (PR) at 8 wks that was durable for 20 wks. Nine pts (31%) experienced disease stabilization at 8 wks, with 6 of 9 exhibiting durable disease control at 6 months. Of the 7 pts with ccRCC in the dose-escalation portion of the trial, 3 (43%) experienced durable disease control for ≥20 wks (range: 20-32). With doses up to 20 mg/kg, SRF388 PK remain linear with an estimated T1/2 of 10-12 days. PK characteristics and safety profile support dosing every 3 or 4 wks. Based on safety, tolerability, PK, peripheral pSTAT1 inhibition, and preliminary efficacy, 10 mg/kg was selected as the RP2D. Both the pembrolizumab safety cohort (n = 10) and Stage 1 of the ccRCC monotherapy expansion (n = 17) have fully enrolled. Of the 10 evaluable pts with ccRCC, 1 confirmed monotherapy PR has been reported, enabling Stage 2 initiation. Changes in several serum cytokines and chemokines were observed after SRF388 administration, including expected increase in circulating IL-27 levels. Conclusions: Results of IL-27 pathway blockade with a first-in-class therapeutic demonstrates that SRF388 has good tolerability with encouraging preliminary antitumor activity as a monotherapy. Updated data, including safety and clinical outcomes as well as correlative biomarker analyses, will be presented. Clinical trial information: NCT04374877.