HER2-positive Advanced Gastric Cancer Research Articles

Human epidermal growth factor receptor 2 (HER2) in advanced gastric cancer: where do we stand?

Gastric cancer is one of the most common malignancy worldwide. In unresectable or metastatic disease, the prognosis is poor and in generally less than a year. HER2 expression remains an important biomarker to lead the addition of trastuzumab to first-line systemic chemotherapy in unresectable or metastatic gastroesophageal adenocarcinoma. To date, a major issue is represented by resistance to trastuzumab developed during treatment, considering the not improved outcomes in this molecular subtype of gastroesophageal adenocarcinoma to other HER2 target strategies. In this review, we summarize the available data on the mechanisms underlying primary and secondary resistance to HER2-targeted therapy and current challenges in the treatment of HER2-positive advanced gastric cancer refractory to trastuzumab. Furthermore, we describe the prognostic value of new non-invasive screening methods, under development novel agents (e.g., HER2 antibody-drug conjugates and bispecific antibodies) and strategies with antitumor activity in early studies.

Trastuzumab deruxtecan for the treatment of HER2-positive advanced gastric cancer: a clinical perspective.

Human epidermal growth factor receptor 2 (HER2)-positive gastric cancer is a subtype for which new drugs and specific treatment strategies should be developed. Trastuzumab deruxtecan (T-DXd) is a novel HER2-targeted antibody-drug conjugate containing topoisomerase I inhibitor as a payload. In the randomized phase 2 study (DESTINY-Gastric01) for HER2-positive advanced gastric or gastroesophageal junction cancer (AGC), patients treated with T-DXd showed a significantly higher response rate compared with the chemotherapy of physician's choice, associated with remarkably prolonged progression-free and overall survival. T-DXd also exhibits anti-tumor activity to HER2-negative tumor cells close to HER2-positive cells (so-called bystander killing effect). T-DXd was effective even for HER2-low expressing breast and gastric cancer in several clinical studies. Taking advantage of these strong points and synergism with other cytotoxic, molecular-targeted and immunological agents, it is expected that T-DXd will bring further progression in treatment both for strongly and weakly HER2 positive AGC in various treatment settings including perioperative chemotherapy.

Trastuzumab ± Capecitabine Maintenance After the First-Line Treatment of HER2-Positive Advanced Gastric Cancer: Retrospective Observational Real-Life Data of Turkish Oncology Group.

In the ToGA trial for HER2-positive advanced gastric cancer, cisplatin plus fluoropyrimidine was given for 6 cycles; trastuzumab was given until disease progression. However, there is a lack of real-life data about trastuzumab maintenance after 6 cycle chemotherapy. This study aims to present real-life data of trastuzumab ± capecitabine maintenance after 6 cycles of platinum, fluoropyrimidine, and trastuzumab in non-progressive patients. This is a retrospective multicenter study of the Turkish Oncology Group. A total of 35 HER2-positive, inoperable locally advanced, recurrent, or metastatic gastric adenocarcinoma patients being non-progressive at the end of 6 cycle chemotherapy and being given trastuzumab ± capecitabine as maintenance treatment were included from sixteen oncology centers. Baseline characteristics, objective tumor responses, progression free and overall survival data, and toxicities were determined. About 68% of the patients were given CF, and 32% were given FOLFOX with trastuzumab as the first-line treatment. The best response in 6 cycle chemotherapy was complete 8 (22%), partial 24 (68%), and stable disease 3 (8%). All patients had trastuzumab maintenance (median cycle 13; range 7-51), and 49% of the patients had capecitabine with trastuzumab (median capecitabine cycle 6; range 2-30). The median PFS of the patients was 12.0months (95% CI 10.3-13.7), and median OS was 17.4months (95% CI 15.2-19.5). There were 2 patients with grade 1 cardiotoxicity. Trastuzumab maintenance ± capecitabine after 6 cycles of trastuzumab plus combined chemotherapy treatment revealed efficacy and safety in non-progressive HER2-positive advanced gastric cancer.

Trastuzumab + FOLFOX6/FLOT as perioperative therapy for HER2-positive resectable gastric cancer and cardioesophageal transition: RussTrastPraсtik study (interim analysis)

Objective. The aim of this study was to evaluate the efficacy and safety of trastuzumab in combination with the FLOT/FOLFOX regimen in the perioperative treatment of resectable HER2-positive locally advanced gastric cancer. Methods. 15 patients were included in two groups; 4 patients were treated with trastuzumab (Herticad®, BIOCAD) + FLOT and 11 patients were treated with trastuzumab (Herticad®, BIOCAD) in combination with FOLFOX. The primary endpoint was incidence of disease stage reduction, tumor regression rate (TRG), change in HER2 tumor status, disease-free and overall survival. Results. Тrastuzumab in combination with FLOT/FOLFOX has a good therapeutic effect and a safety profile in the perioperative treatment of patients with resectable HER2-positive advanced gastric cancer (complete tumor regression [TRG1] was morphologically confirmed in 20% of patients, no pathomorphosis or minimal manifestations [TRG3/TRG4] in 40% of patients, in 40% of patients it was possible to achieve significant pathomorphological tumor regression [TRG2]). In addition, trastuzumab + FLOT gives better results in terms of tumor regression rate than FOLFOX + trastuzumab (cN+/ypN0 disease stage reduction in the T + FLOT group was 100%, whereas in the T + FOLFOX group it was only 30.0%). The HER2 status of the tumor changes against the background of preoperative PCT with the inclusion of trastuzumab (a loss of HER2/ neu protein overexpression was detected in 60% of patients).

A multi-institutional phase Ib/II trial of first-line triplet regimen (Pembrolizumab, Trastuzumab, Chemotherapy) for HER2-positive advanced gastric and gastroesophageal junction cancer (PANTHERA Trial): Molecular profiling and clinical update.

218 Background: We report the updated clinical data and molecular profiling results of a multi-institutional phase Ib/II trial of triple combination (pembrolizumab, trastuzumab, and chempotherapy) as first line therapy for HER2 positive advanced gastric and gastroesophageal junction (AGC/GEJ) cancer. (PANTHERA trial; NCT02901301). Methods: Pembrolizumab 200mg IV D1, Trastuzumab 6mg/kg (after 8mg/kg load) D1, Capecitabine 1000mg/m2 bid D1-14, and Cisplatin 80mg/m2 D1 every 3 weeks was selected as recommended phase II dose. The primary endpoint for phase II was ORR per RECIST v1.1. Secondary endpoints included PFS, OS, DOR, safety, and predictive biomarker analysis by targeted NGS. Results: At the time of data lock on Aug 31, 2020, total of 43 patients were treated with median follow up of 18.2 months, and 3 patients remained on the treatment, and 6 patients finished 2-year treatment without progression. ORR was 76.7% (CR 16.3%, PR 60.5%, conversion surgery 4.6%) with 26 pts (56.6%) showing more than 50% of tumor burden reduction. Median PFS was 8.6 months (95% CI 7.2-16.5) and median OS was 19.3 months (95% CI 16.5-NR). There were no MSI-H/dMMR or EBV-positive pts. No patient discontinued pembrolizumab because of immune-related adverse events. Clinical features including PD-L1 status (55.3% of pts ≥ CPS 1 and 13.2% of pts ≥ CPS 10 among available 38 pts), metastatic organ or baseline tumor burden was not related to the survival. Ninety-eight tumor tissues from 39 pts (paired tumor tissues from 22 pts) were analyzed with targeted NGS. Although every pts were HER2 IHC-positive, baseline HER2 amplification by NGS was related to the survival ( HER2 amp (n=8) vs HER2 non-amp (n=23); mPFS, not reached vs 7.7 months, P=0.0178; mOS, not reached vs 17.9 months, P=0.044) but no other signaling pathways predicted pts’ survival. HER2 mutations including L869R or D769H were related to the acquired resistance. High TMB showed a tendency toward better survival (mPFS; High (n=7) vs Low (n=24) TMB, 22.0 vs 8.2, P=0.2835) due to small number of patients. Updated immune markers and serial NGS analyses will be presented. Conclusions: First-line triplet regimen (Pembrolizumab, Trastuzumab, and Chemotherapy) showed promising efficacy based on HER2 amplification by NGS regardless of PD-L1 status in AGC/GEJ cancer. Correlative biomarkers found from NGS study need to be validated through on-going phase III Keynote-811 study. Clinical trial information: NCT02901301. [Table: see text]

Perioperative trastuzumab, capecitabine and oxaliplatin in patients with HER2-positive resectable gastric or gastro-oesophageal junction adenocarcinoma: NEOHX phase II trial

IntroductionPerioperative chemotherapy improves overall survival (OS) and disease-free survival (DFS) compared with surgery alone in patients with resectable gastric adenocarcinoma (GA) or gastro-oesophageal junction adenocarcinoma (GEJA). The addition of trastuzumab to chemotherapy improves outcomes in patients with HER2-positive advanced gastric cancer (GC), and we aimed to explore its role in the perioperative setting. Material and methodsThis Spanish, multicentre, open-label phase II trial evaluated the efficacy and toxicity of perioperative capecitabine, oxaliplatin and trastuzumab (XELOX-T) in patients with HER2-positive resectable GA or GEJA. The primary end-point was 18-months DFS; and secondary end-points included pathological complete response (pCR) rate, R0 resection rate, OS and toxicity (NCT01130337). ResultsThirty-six patients were included. After three cycles of preoperative treatment, 14 patients (38% of the intention-to-treat population) had partial response and 18 (50%) had stable disease. Surgery was performed in 31 patients: 28 (90%) had R0 resection, three (9.6%) had a pCR and three (9.6%) died due to surgical complications. A total of 24 patients received post-operative XELOX-T, 22 of whom completed trastuzumab maintenance. Main grade III/IV toxicities included diarrhoea (33%), nausea and vomiting (8%). After a median follow-up of 24.1 months, 18-month DFS was 71% (95% confidence interval [CI], 53–83%); and an update after 102 months of follow-up showed a median OS of 79.9 months and a 60-month OS of 58% (95% CI, 40–73%). ConclusionsThese data suggest that perioperative XELOX-T in patients with HER2-positive GA and GEJA is feasible and active. Further investigation in randomised studies is warranted.

Trastuzumab deruxtecan for the treatment of patients with HER2-positive gastric cancer

Trastuzumab deruxtecan (T-DXd) is a novel anti-human epidermal growth factor receptor 2 (HER2) antibody–drug conjugate composed of a monoclonal anti-HER2 antibody and a topoisomerase I inhibitor, DX-8951 derivative (an exatecan derivative). T-DXd showed potential anti-tumor activities in HER2-positive gastric cancer cell lines and xenograft models. In the randomized, phase II trial DESTINY-Gastric01, T-DXd demonstrated a significantly higher objective response rate as a primary endpoint and a longer overall survival as a secondary endpoint in patients with pretreated HER2-positive advanced gastric cancer (AGC). Although adverse events caused by T-DXd were generally manageable, approximately 10% of patients experienced treatment-related interstitial lung disease. Based on the results of the DESTINY-Gastric01 trial, T-DXd was approved for HER2-positive pretreated AGC in Japan. This study reviews the preclinical and clinical data of T-DXd for treating HER2-positive gastric cancer.

Combination of trastuzumab and taxane-containing intensified chemotherapy in first-line treatment of HER2-positive advanced gastric cancer.

Taxane-containing combinations are recommended for the first-line therapy of advanced gastric cancer. It is not known which chemotherapy regimen is the best with trastuzumab for HER2-positive patients. The aim of this study was to compare taxane-containing intensified chemotherapy versus standard chemotherapy in combination with trastuzumab in the first-line treatment of HER2-positive advanced gastric adenocarcinoma. This study is a retrospective multicenter study of the Turkish Oncology Group. A total of 130 HER2-positive patients with inoperable locally advanced, recurrent, or metastatic gastric adenocarcinoma being given chemotherapy plus trastuzumab as the first-line treatment were included from 16 different oncology centers. Trastuzumab combination with intensified chemotherapy including taxane or standard chemotherapy was compared in terms of progression-free survival (PFS), overall survival (OS), and toxicity. There were 108 patients in the standard and 22 patients in the intensified chemotherapy group. PFS of the standard and intensified group were 5.6 months (95% confidence interval [CI] 4.8-6.4) and 5.3 months (95% CI 2.6-8), respectively (p = 0.70). OS of the standard and intensified group were 11.1 months (95% CI 8.3-13.9) and 15.2 months (95% CI 12.7-17.7), respectively (p = 0.03). Repeated analysis excluding patients given any previous therapy revealed similar results. The intensified group had more fever and febrile neutropenia. Trastuzumab combination with intensified chemotherapy provides better OS in first-line treatment of HER2-positive advanced gastric cancer. Further large-scale studies should be performed in HER2-positive patients.

158P A phase II study of trastuzumab with S-1 plus oxaliplatin for HER2-positive advanced gastric cancer (HIGHSOX study): Final report

158P A phase II study of trastuzumab with S-1 plus oxaliplatin for HER2-positive advanced gastric cancer (HIGHSOX study): Final report

Trastuzumab Deruxtecan in Previously Treated HER2-Positive Gastric Cancer

BackgroundTrastuzumab deruxtecan (DS-8201) is an antibody-drug conjugate consisting of an anti-HER2 (human epidermal growth factor receptor 2) antibody, a cleavable tetrapeptide-based linker, and a cytotoxic topoisomerase I inhibitor. The drug may have efficacy in patients with HER2-positive advanced gastric cancer.MethodsIn an open-label, randomized, phase 2 trial, we evaluated trastuzumab deruxtecan as compared with chemotherapy in patients with HER2-positive advanced gastric cancer. Patients with centrally confirmed HER2-positive gastric or gastroesophageal junction adenocarcinoma that had progressed while they were receiving at least two previous therapies, including trastuzumab, were randomly assigned in a 2:1 ratio to receive trastuzumab deruxtecan (6.4 mg per kilogram of body weight every 3 weeks) or physician’s choice of chemotherapy. The primary end point was the objective response, according to independent central review. Secondary end points included overall survival, response duration, progression-free survival, confirmed response (response persisting ≥4 weeks), and safety.ResultsOf 187 treated patients, 125 received trastuzumab deruxtecan and 62 chemotherapy (55 received irinotecan and 7 paclitaxel). An objective response was reported in 51% of the patients in the trastuzumab deruxtecan group, as compared with 14% of those in the physician’s choice group (P<0.001). Overall survival was longer with trastuzumab deruxtecan than with chemotherapy (median, 12.5 vs. 8.4 months; hazard ratio for death, 0.59; 95% confidence interval, 0.39 to 0.88; P=0.01, which crossed the prespecified O’Brien–Fleming boundary [0.0202 on the basis of number of deaths]). The most common adverse events of grade 3 or higher were a decreased neutrophil count (in 51% of the trastuzumab deruxtecan group and 24% of the physician’s choice group), anemia (38% and 23%, respectively), and decreased white-cell count (21% and 11%). A total of 12 patients had trastuzumab deruxtecan–related interstitial lung disease or pneumonitis (grade 1 or 2 in 9 patients and grade 3 or 4 in 3), as adjudicated by an independent committee. One drug-related death (due to pneumonia) was noted in the trastuzumab deruxtecan group; no drug-related deaths occurred in the physician’s choice group.ConclusionsTherapy with trastuzumab deruxtecan led to significant improvements in response and overall survival, as compared with standard therapies, among patients with HER2-positive gastric cancer. Myelosuppression and interstitial lung disease were the notable toxic effects. (Funded by Daiichi Sankyo; DESTINY-Gastric01 ClinicalTrials.gov number, NCT03329690.)

First-in-human phase I study of BVAC-B cell therapy in HER2-positive advanced gastric cancer.

4534 Background: BVAC-B is an autologous B cell- and monocyte-based immunotherapeutic vaccine transfected with recombinant HER2/neu gene and loaded with alpha-galactosyl ceramide, a natural killer T cell ligand. It may have activity against HER2/neu positive cancer. Preclinical data in mouse models have shown promising anti-tumor activity by eliciting broad spectrum of immune responses against HER2/neu positive tumor cells. We report here the results of phase 1 study of BVAC-B in HER2 positive advanced gastric cancer. Methods: Metastatic gastric cancer with IHC &gt; 1+ of HER2/neu were eligible for enrollment. Two weeks before treatment, subjects were admitted to hospital for collection of PBMC and plasma by lymphapheresis. The PBMC were sent to Cellid for vaccine manufacturing which took a day. BVAC-B was given intravenously at 0, 4, 8, and 12 weeks. Subjects received low (2.5X 107 cells/dose), medium (5.0X 107 cells/dose) or high dose (1.0X 108 cells/dose). Endpoints included safety, tolerability and MTD for phase 2 trial. Exploratory outcomes included immune responses after BVAC-B administration. Results: As of January 29, 2020, 8 subjects were treated with BVAC-B at doses of 2.5X 107 cells/dose (n=1), 5.0X 107 cells/dose (n=1) and 1.0X 108 cells/dose (n=6). Median line of therapy at which BVAC-B was administered was 4 (range, 2-9). Mean duration treatment was 1.8 (range 1-4) cycles. The most common treatment related adverse events were fever (n=4, 50%). One subject enrolled in medium dose experienced cytokine release syndrome (G2) with high fever (39.3℃) and hypotension 8 hours after first administration, but was manageable with hydration and supportive management. Other adverse events included increase of AST and ALT (G1, n=1 and G2, n=2), and hypotension (G1, n=1). There were no adverse events which led to treatment discontinuation. Immunologic response analysis showed that BVAC-B induced activation of natural killer T cells, natural killer cells, HER2/neu specific T cells, and release of HER2/neu specific antibody upon vaccinations in few patients who were evaluated. Conclusions: BVAC B is feasible and has acceptable toxicity profile. We considered all dose evaluated in this study available for phase 2 study, given that the maximum tolerated dose is expected to exceed the maximum dose administered in this study. For clinically relevant effect, further studies are warranted, including earlier line of exposure to BVAC-B as well as combination treatments. Clinical trial information: NCT03425773 .

A phase Ib study of nivolumab plus trastuzumab with S-1/capecitabine plus oxaliplatin for HER2-positive advanced gastric cancer (Ni-HIGH study): Safety evaluation.

4525 Background: Addition of an anti-PD-1 antibody to trastuzumab (Tmab) reportedly enhances ADCC activity of Tmab, leading to an additive antitumor effect. We investigated the safety and tolerability of nivolumab (Nivo) plus Tmab combined with S-1 or capecitabine (Cape) and oxaliplatin (Ox) for pts with HER2-positive (+) advanced gastric cancer (AGC). Here, we report the safety evaluation results. Methods: This open-label, phase 1b study was conducted at four centers in Japan. The study consisted of safety (n = 12) and expansion (n = 24–30) parts. Chemotherapy-naïve pts aged ≥ 20 years with histopathologically confirmed HER2+ AGC and measurable lesions were eligible. In the safety evaluation, pts were assigned to cohort 1 or 2 in sequence. Pts received Nivo (360 mg, day 1), Tmab (course 1: 8 mg/kg; course 2–: 6 mg/kg, day 1), Ox (130 mg/m2, day 1) and either S-1 (40 mg/m2 bid, days 1–14; cohort 1) or Cape (1000 mg/m2 bid, days 1–14; cohort 2) every 3 weeks until disease progression or unacceptable toxicity. The primary purpose of the safety evaluation was to determine the toxicity and tolerability of this combination therapy. An independent data and safety monitoring committee assessed the tolerability of the study treatments before starting the second treatment course. A preliminary evaluation of tumor response on the cut-off date (December 16, 2019) was also performed. Results: From November 2018 to August 2019, 12 pts with HER2+ AGC were enrolled in the safety part (six pts each in cohorts 1 and 2). During the 1st course, all 12 pts experienced at least one adverse event (AE). The most common AEs were peripheral sensory neuropathy (PSN) (n = 4) and leukocytopenia (n = 3) in cohort 1 and PSN (n = 5) and anorexia (n = 4) in cohort 2. AEs of grade ≥ 3 were observed in only one pt in cohort 1 (grade 3 neutropenia). No pt suspended or discontinued study treatments due to AEs. One pt in cohort 1 reduced dose of S-1 due to grade 2 erythema and continued the subsequent courses with the dose. After a median follow-up of 6.1 (range, 3.1–13.3) months, one pt from cohort 1 achieved a complete response, eight pts (four in each cohort) achieved a partial response, and three pts (one in cohort 1 and two in cohort 2) showed stable disease. No progressive disease was observed. Conclusions: Both Nivo plus Tmab and either S-1 or Cape plus Ox are tolerable in pts with HER2+ AGC. Both cohorts 1 and 2 have progressed to the expansion part of the study. Clinical trial information: 000034222 .

Changing HER2-status of the primary gastric tumor after neoadjuvant trastuzumab-based therapy.

e16529 Background: Aproximetly 16 % of patients with metastatic gastric cancer (GC) have HER2+ tumors. With localized stages, the detection rate of HER2+ is known to be lower. Addition of trastuzumab (T) to chemotherapy (CT) improved survival in metastatic, HER2+ GC. Unlike the metastatic disease, Her-2 did not represent an independent prognostic biomarker for early stages during exploratory analysis of MAGIC trial. The aim of the study was to compare human epidermal growth factor receptor 2 (HER2) expression before and after trastuzumab-based chemotherapy in patients with locally advanced HER2-positive gastric cancer, to evaluate the contribution of trastuzumab to the effectiveness of neoadjuvant treatment in this rare patient population. Methods: We assessed HER2 expression using immunohistochemistry in pre-treatment biopsied specimens and post-treatment resected specimens obtained from 10 patients with locally advanced HER2-positive (3+) gastric cancer receiving trastuzumab-based neoadjuvant chemotherapy: 8 men (80%) and 2 women (20%), from 30 to 80 years old, the median age was 63,5 years. Included 7 patients with resectable adenocarcinoma of the stomach and 3 patients with adenocarcinoma of the esophageal-gastric junction. All patients received neoadjuvant therapy with trastuzumab (100%) + chemotherapy: FLOT (2 patients), FOLFOX (7 patients), XELOX (1 patient). All patients underwent R0 gastrectomy. Tumor regression grading (TRG) after treatment were determined according to Mandard system. Results: Two patients showed a complete pathomorphological response of the tumor (20%,TRG1), therefore, the determination of postoperative HER2 status was not possible. Two patients (20%) maintained the HER2-positive status and six patients (60%) had a change in HER2 expression from positive to negative. Three patients had a (y)pT3 and 5 had a (y)pN+ tumor. Basing on histological changes the tumor regression TRG3 ( &lt; 10% residual tumor cells) was observed in 5 patients (50%). TRG 4-5(preponderance of tumor cells/tumors without changes of regression) observed in 3 patients (30%). The follow-up period is too short for disease-free survival or overall survival to be assessed. Conclusions: HER2 expression can change after trastuzumab-based chemotherapy in patients with locally advanced HER2-positive gastric cancer. Continuous monitoring of HER2 expression after neoadjuvant treatments may be utilized to determine whether the continued use of trastuzumab is advisable.

Targeting HER2 in combination with anti-PD-1 and chemotherapy confers a significant tumor shrinkage of gastric cancer: A multi-institutional phase Ib/II trial of first-line triplet regimen (pembrolizumab, trastuzumab, chemotherapy) for HER2-positive advanced gastric cancer (AGC).

3081 Background: Combining anti-PD-1 agent and trastuzumab has shown synergy in HER2 positive preclinical cancer models. We first report the result of a multi-institutional phase Ib/II trial of triple combination (pembrolizumab, trastuzumab, and chempotherapy) as first line therapy for HER2 positive AGC. (PANTHERA trial; NCT02901301). Methods: Pembrolizumab 200mg IV D1, Trastuzumab 6mg/kg (after 8mg/kg load) D1, Capecitabine 1000mg/m2 bid D1-14, and Cisplatin 80mg/m2 D1 every 3 weeks was selected as recommended phase II dose. The primary endpoint for phase II was ORR per RECIST v1.1. Secondary endpoints included PFS, OS, DoR, safety, and molecular analysis by targeted NGS. Results: Total of 43 patients were treated with median follow up of 16.1 months, and 11 pts remained on the treatment (treatment duration range: 1.4 to 24 months). There was significant tumor shrinkage of 95.3% with 54.6% median depth of response, with 76.7% ORR (CR 16.3%, PR 60.5%, conversion surgery 4.6%), and 97.7% DCR. Median PFS was 8.6 months (95% CI 7.2-22.0) and median OS was 18.4 months (95% CI 17.9-NA). Subsequent chemotherapy was given to 83.3% of 30 progressed pts. There were no MSI-H/dMMR or EBV-positive pts. PD-L1 status (57.1% of pts ≥ CPS 1 and 14.3% of pts ≥ CPS 10 among 35 pts), metastatic organ or baseline tumor burden was not related to the survival. Treatment-related AE (≥G3) occurred in 32 pts (74.4%) including 17 pts (39.5%) with neutropenia G3-4. Immune-related AEs (≥G3) occurred in 4 pts (10%). Ninety-six tumor tissues from 32 pts (paired tumor tissues from 25 pts) were analyzed with targeted NGS. TMB (median 12.7 mut/MB with range of 9.45-16.71) was not related to the PD-L1 expression or survival. Conclusions: First-line triplet regimen (Pembrolizumab, Trastuzumab, and Chemotherapy) confers a significant tumor shrinkage for HER2 positive AGC, regardless of PD-L1 status. Phase III Keynote-811 study (NCT03615326) is ongoing based on the protocol of this study. Clinical trial information: NCT02901301 . [Table: see text]

Human Epidermal Growth Factor Receptor 2 (HER2) in Advanced Gastric Cancer: Current Knowledge and Future Perspectives.

The discovery of human epidermal growth factor receptor 2 (HER2) overexpression in 15-20% of gastric adenocarcinomas has been a key advance in the global care of this disease. Validated by the ToGA trial in the first-line setting of advanced HER2-positive (+) gastric cancer (GC), trastuzumab, an anti-HER2 monoclonal antibody (mAb), was the first therapeutic agent to significantly improve the prognosis of these patients. Since these results, many attempts have been made to improve the clinical outcomes of patients with HER2+ GC. However, all the other HER2-targeting molecules have failed to show a survival benefit in large phase III studies. The value of continuing trastuzumab after disease progression has been suggested by several retrospective studies. However, recent results of a randomized phase II trial showed no benefit from this strategy. On the other hand, novel therapeutic methods, such as immunotherapy, are emerging as new tools in the strategy of care of advanced GC, even if their benefit in the specific HER2+ population remains undetermined. Furthermore, substantial progress has been made in the understanding of the mechanisms leading to resistance to anti-HER2 therapies, and in the screening methods to detect them, thus opening new perspectives. The aim of this review was firstly to summarize the existing data on the specific strategy of care of HER2+ advanced GC, and secondly, to describe current knowledge regarding the potential mechanisms of resistance to HER2-targeting therapies. Lastly, we report the prospects for overcoming these potential obstacles, from future therapeutic strategies to new detection methods.

Emerging Targeted Therapies for HER2 Positive Gastric Cancer That Can Overcome Trastuzumab Resistance.

Trastuzumab, a monoclonal antibody to human epidermal growth factor receptor 2 (HER2), has improved survival in patients with HER2-positive advanced gastric or gastroesophageal junction cancer (AGC). The inevitable development of resistance to trastuzumab remains a problem, however, with several treatment strategies that have proven effective in breast cancer having failed to show clinical benefit in AGC. In this review, we summarize the mechanisms underlying resistance to HER2-targeted therapy and outline past and current challenges in the treatment of HER2-positive AGC refractory to trastuzumab. We further describe novel agents such as HER2 antibody–drug conjugates that are under development and have shown promising antitumor activity in early studies.

A Case of HER2-positive Advanced Gastric Cancer Successfully Resected by Conversion Surgery after SOX/Trastuzumab Combination Therapy

A Case of HER2-positive Advanced Gastric Cancer Successfully Resected by Conversion Surgery after SOX/Trastuzumab Combination Therapy

Comparison of HER2 Status Before and After Trastuzumab-based Chemotherapy in Patients With Advanced Gastric Cancer.

The aim of the present study was to compare human epidermal growth factor receptor 2 (HER2) expression before and after trastuzumab-based chemotherapy in patients with advanced HER2-positive gastric cancer. We assessed HER2 expression using immunohistochemistry and/or fluorescence in situ hybridization in pre-treatment biopsied specimens and post-treatment resected specimens obtained from seven patients with advanced HER2-positive gastric cancer receiving trastuzumab-based chemotherapy. Four patients maintained the HER2-positive status and three patients had a change in HER2 expression from positive to negative. In patients showing the loss of HER2 expression after treatments, HER2-positive tumor cells with a dominant histological type disappeared, and HER2-negative tumor cells with another dominant histological type were identified. HER2 expression can change after trastuzumab-based chemotherapy in patients with advanced HER2-positive gastric cancer. Continuous monitoring of HER2 expression after treatments may be utilized to determine whether the continued use of trastuzumab is advisable.

Abstract B049: Hyperprogressive disease after two cycles of immunotherapy in HER-2 positive metastatic gastric cancer

Abstract Background: Recent advancements in immune checkpoint inhibitors (ICIs) have revolutionized treatment options in many solid cancers. Pembrolizumab and nivolumab, an anti-programmed death ligand 1 (anti PD-L1) agent, has approved in treatment of advanced or metastatic gastric cancer previously treated with two or more therapies. Although immunotherapy has shown durable response in selective patients, there are also growing evidences of hyperprogression (HPD) in a subset of patients treated with ICIs. Here, we report a patient who hyper-progressed after two cycles of pembrolizumab containing regimen. Methods: Based on Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, HPD is defined as time to treatment failure (TTF) &amp;lt;2 months and minimum increase of measurable lesions of 10mm plus one of the following: 1) increase of &amp;gt;40% of target lesion compared with baseline or 2) increase of &amp;gt;20% and appearance of multiple new lesions. Medical records of the patient were retrieved from electronic medical record (EMR). Tumor samples were obtained from stomach and liver before and after anti-PD1 treatment. Serial blood was collected to evaluate circulating tumor cells (CTC), targeted NGS of circulating free DNA (cfDNA) and immune phenotyping to identify possible underlying mechanism. To identify the mechanisms of HPD, Next-Generation Sequencing (NSG) of tissue and cfDNA of FoundationOne Liquid was utilized to analyze genomic alterations such as copy number alterations, rearrangements somatic mutations. Results: The 57 year old female, was initially diagnosed with HER2 positive advanced gastric cancer (AGC) with multiple liver metastases. Before treatment, immunohistochemistry (IHC) from stomach revealed amplification of human epidermal growth factor receptor 2 (HER2, ERbB2) with combined positive score (CPS) of 10% using PD-L1 IHC 22C3 pharmDx. She was then enrolled in the currently ongoing, investigator-initiated PANTHERA trial (NCT02901301), a phase Ib/II study of first line pembrolizumab in combination with trastuzumab, capecitabine and cisplatin. However, rapid progression was noted after two cycles. Target lesions increased by 27.1%, and several new liver metastasis as well as non-targetable lesions such as stomach and peritoneal seeding, increased. Tumor markers including CA 72-4, CA 125 and aFP also increased. Since the patient’s condition deteriorated rapidly, she was immediately started with a different chemotherapy and response evaluation with immune-related Response Evaluation Criteria in Solid Tumors (irRECIST) was not evaluated. IHC of re-biopsied stomach revealed that CPS was 30%. Notably, there were no differences in IHC of liver before and after treatment, which were both HER2 and CPS negative. Interestingly, baseline cfDNA analysis showed the amplification of EGFR, which were known to be related to HPD. Also, high level of TP53, APC mutations and Rb amplification were observed. CTC (EpCAM+CK+CD45) was initially 2 at baseline and increased to 7 after hyperprogression. Conclusion: Among 41 patients enrolled in ongoing PANTHERA trial, only one patient progressed after 2 cycles of treatment . To our knowledge, this is the first documented hyperprogression in advanced or metastatic gastric cancer after treatment with pembrolizumab. Although mechanisms behind HPD remain to be elucidated, the discrepancy in pre and post IHC results points out that tumor heterogeneity may play a role. NGS results and immune phenotyping results are pending. Citation Format: Jii Bum Lee, Garden Lee, Woo Sun Kwon, Jun Hyeok Heo, Seung-Hyun Jung, Yeun-Jun Chung, Beodul Kang, Hyo Song Kim, Hyun Cheol Chung, Sun Young Rha. Hyperprogressive disease after two cycles of immunotherapy in HER-2 positive metastatic gastric cancer [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 B049. doi:10.1158/1535-7163.TARG-19-B049

137P - Significant benefit of pyrotinib combined with SHR6390 in patients with multiline-resistant HER2-positive advanced gastric cancer

BackgroundThe aim of the present study was to explore the mechanism underlying the poor efficacy of pyrotinib, propose and validate a strategy for pyrotinib-combined therapy in patients with human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC). MethodsHuman GC cell lines and patient-derived xenograft (PDX) models were used to evaluate the antitumor activity and mechanisms of pyrotinib. One pyrotinib-refractory PDX model was established to explore the potential mechanisms underlying drug resistance, propose an optimal therapeutic strategy, and further validate in a phase I clinical trial (NCT03480256). ResultsPyrotinib exerted strong antitumor activity in HER2-positive GC cells and PDX models via suppressing the activation of the AKT/S6 signaling pathway. In addition, dysregulation of the cell cycle, represented by aberrant activation of the CCND1-CDK4/6-Rb axis, was found in the pyrotinib-refractory PDX model compared with the parental model. Then, combination therapy of pyrotinib with a CDK4/6 inhibitor (SHR6390) was proposed and its strong tumor growth inhibition was observed in the pyrotinib refractory-PDX model. Three HER2-positive GC patients after multiline therapies were subsequently enrolled in our clinical trial treatment with pyrotinib (400 mg/d for 28 days per cycle) combined with SHR6390 (100 mg/d for 21 days per cycle). After two cycles of therapy, two patients achieved a partial response (PR) and one patient achieved decreased stable disease (SD) with a progression-free survival of 120, 199, and 110 d, respectively. The common adverse events included leucopenia (grade 2 to 3), neutropenia (grade 2 to 4), anemia (grade 1 to 3), and thrombocytopenia (grade 1). ConclusionsThis representative translational study suggests that a combination treatment of pyrotinib with SHR6390 may serve as a promising strategy for patients with HER2-positive GC after systematic treatment failure. The optimal drug doses and tolerability of this combination treatment will be explored in future studies. Legal entity responsible for the studyZuhua Chen. FundingThe National Key Research and Development Program of China (No. 2017YFC1308900, 2017YFC0908400). DisclosureAll authors have declared no conflicts of interest.