SEAMARK: phase II study of first-line encorafenib and cetuximab plus pembrolizumab for MSI-H/dMMR BRAFV600E-mutant mCRC

Patients with both BRAF V600E mutations and microsatellite instability-high (MSI-H)/mismatch repair-deficient (dMMR) metastatic colorectal cancer (mCRC) have poor prognosis. Currently, there are no specifically targeted first-line treatment options indicated for patients with mCRC whose tumors harbor both molecular aberrations. Pembrolizumab is a checkpoint inhibitor approved for the treatment of MSI-H/dMMR mCRC, and the BRAF inhibitor encorafenib, in combination with cetuximab, is approved for previously treated BRAF V600E-mutant mCRC. Combination of pembrolizumab with encorafenib and cetuximab may synergistically enhance antitumor activity in patients with BRAF V600E-mutant, MSI-H/dMMR mCRC. SEAMARK is a randomized phase II study comparing the efficacy of the combination of pembrolizumab with encorafenib and cetuximab versus pembrolizumab alone in patients with previously untreated BRAF V600E-mutant, MSI-H/dMMR mCRC.

Abstract CT201: Phase Ib/II open-label, randomized evaluation of atezolizumab + cobimetinib vs control in MORPHEUS-NSCLC (non-small cell lung cancer), MORPHEUS-PDAC (pancreatic ductal adenocarcinoma) and MORPHEUS-GC (gastric cancer)

Background: The MORPHEUS platform comprises multiple Phase Ib/II trials to identify early efficacy signals and safety of treatment combinations across cancers. Within MORPHEUS, atezolizumab (atezo), a PD-L1 inhibitor, was tested in combination with cobimetinib (cobi), a MEK1/2 inhibitor, in patients with advanced/metastatic (m) NSCLC, PDAC or GC. Methods: MORPHEUS-NSCLC (NCT03337698) enrolled patients who had disease progression during or after receiving a platinum-based regimen and a PD-L1/PD-1 checkpoint inhibitor. MORPHEUS-PDAC (NCT03193190) enrolled patients who had received 1 prior line of systematic therapy. MORPHEUS-GC (NCT03281369) enrolled HER2-negative patients who had not received prior chemotherapy. Patients enrolled in the atezo + cobi arms received atezo 840 mg q2w and cobi 40 mg daily on days 1-21 of each 28-day cycle. In MORPHEUS-GC, patients in the atezo + cobi arm also received mFOLFOX6. This arm started with a safety run-in during which cobi 40 mg could be dose escalated to 60 mg. Control treatments were docetaxel (75 mg/m2) in MORPHEUS-NSCLC and mFOLFOX6 or gemcitabine (100 mg/m2) plus nab-paclitaxel (125 mg/m2) in MORPHEUS-PDAC. The MORPHEUS-GC safety run-in did not have a control. Primary endpoints were objective response rate (ORR; investigator-assessed RECIST 1.1) and safety. Results: MORPHEUS-NSCLC (data cutoff, April 10, 2019): 15 patients received atezo + cobi, and 14 patients received control treatment. No responses were observed, and 7 patients had stable disease (SD) as best response in the treatment arm. In the control arm, 3 patients had partial response (PR), and 5 patients had SD as confirmed best response. All treated patients were evaluable for safety, with 67% of atezo + cobi and 93% of control patients experiencing a treatment-related adverse event (TRAE). Updated data from MORPHEUS-NSCLC will be presented. MORPHEUS-PDAC (data cutoff, September 7, 2018): 14 patients received atezo + cobi, and 15 patients received control treatment. There were no responses in either study arm, but 6 patients in the control arm had SD as confirmed best response. All treated patients were evaluable for safety, with 79% of atezo + cobi and 87% of control patients experiencing a TRAE. MORPHEUS-GC (data cutoff, July 11, 2019): 5 patients received atezo + cobi + mFOLFOX6 in the safety run-in after which this arm was terminated (due to internal re-prioritization, no safety concerns identified). Two patients had PR, and 3 patients had SD as confirmed best response. All 5 patients had a TRAE. Biomarker data will also be presented. Conclusions: No superior efficacy signals were identified with atezo + cobi in NSCLC, PDAC or GC. The safety of atezo + cobi was consistent with each agent's known safety profile, with no new safety signals identified.

Citation Format: Byoung Chul Cho, Nathan Bahary, Johanna Bendell, Enriqueta Felip, Melissa Johnson, Yoon-Koo Kang, Farah Louise Lim, Teresa Macarulla, Gulam Manji, Do-Youn Oh, Osama Rahma, Simon Allen, Edward Cha, Denise Cotting, Hans-Joachim Helms, Jan Pintoffl, Pakeeza Sayyed, Xiaosong Zhang, Kyu-pyo Kim. Phase Ib/II open-label, randomized evaluation of atezolizumab + cobimetinib vs control in MORPHEUS-NSCLC (non-small cell lung cancer), MORPHEUS-PDAC (pancreatic ductal adenocarcinoma) and MORPHEUS-GC (gastric cancer) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT201.

Cost-Effectiveness Analysis of Biomarker-Guided Treatment for Metastatic Gastric Cancer in the Second-Line Setting

BACKGROUND

The 5-year survival rate of patients with metastatic gastric cancer (GC) is only 5%. However, trials have demonstrated promising antitumor activity for targeted therapies/immunotherapies among chemorefractory metastatic GC patients. Pembrolizumab has shown particular efficacy among patients with programmed death ligand-1 (PD-L1) expression and high microsatellite instability (MSI-H). The aim of this study was to assess the effectiveness and cost-effectiveness of biomarker-guided second-line GC treatment.

METHODS

We constructed a Markov decision-analytic model using clinical trial data. Our model compared pembrolizumab monotherapy and ramucirumab/paclitaxel combination therapy for all patients and pembrolizumab for patients based on MSI status or PD-L1 expression. Paclitaxel monotherapy and best supportive care for all patients were additional comparators. Costs of drugs, treatment administration, follow-up, and management of adverse events were estimated from a US payer perspective. The primary outcomes were quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs) with a willingness-to-pay threshold of $100,000/QALY over 60 months. Secondary outcomes were unadjusted life years (survival) and costs. Deterministic and probabilistic sensitivity analyses were performed to evaluate model uncertainty.

RESULTS

The most effective strategy was pembrolizumab for MSI-H patients and ramucirumab/paclitaxel for all other patients, adding 3.8 months or 2.0 quality-adjusted months compared to paclitaxel. However, this strategy resulted in a prohibitively high ICER of $1,074,620/QALY. The only cost-effective strategy was paclitaxel monotherapy for all patients, with an ICER of $53,705/QALY.

CONCLUSION

Biomarker-based treatments with targeted therapies/immunotherapies for second-line metastatic GC patients substantially improve unadjusted and quality-adjusted survival but are not cost-effective at current drug prices.