Response to PD-1 inhibitor after progression on PD-L1 inhibitor in advanced HCC.

For hepatocellular carcinoma, the IMbrave150 trial demonstrated that combination atezolizumab and bevacizumab had significantly better overall survival compared with sorafenib in patients with unresectable disease. However, as more immune checkpoint inhibitors are approved as first-line agents in gastrointestinal cancers, there have been few reports on whether sequential PD-1/PD-L1 blockade is beneficial in the treatment of these diseases. We present a patient with hepatocellular carcinoma who had disease progression on atezolizumab, a PD-L1 inhibitor, but subsequently had a remarkable response to pembrolizumab, a PD-1 inhibitor.

Treatment of Metastatic Disease with Immune Checkpoint Inhibitors Nivolumab and Pembrolizumab: Effect of Performance Status on Clinical Outcomes.

Introduction: Although guidelines exist for appropriate use of chemotherapy in the metastatic setting based on performance status, such recommendations are less readily available for immune checkpoint inhibitors (ICIs). We sought to determine whether there is a relationship between Eastern Cooperative Oncology Group (ECOG) performance status and outcomes of immunotherapy in patients treated for metastatic disease at our community-based oncology practice. Methods: Patients (n = 253) were identified as receiving nivolumab or pembrolizumab for stage IV malignancy at Cancer Centers of Colorado, St. Joseph Hospital/SCL Health between June 2018 and November 2020. Patients who initiated therapy after May 2020 were excluded from analysis due to less than 6 months follow-up time. The remaining 183 patients were included in a retrospective cohort study comparing patients with ECOG 0, 1, and 2-4. Sex, age, type of cancer, line of therapy, time on therapy and best response to therapy were determined. These baseline factors and outcomes were compared using analysis of variance (ANOVA) for numeric variables and χ2 tests of association for categorical variables. Time from initiation of ICI to death or hospice was also compared using a log-rank test as well as a multivariate Cox proportional hazards model. Results: Of the 183 patients included, 31.7% had an ECOG of 0, 48.6% an ECOG of 1, and 19.7% an ECOG of 2-4. Non-small cell lung cancer and melanoma represented the majority of patients in each group. Sex and line of therapy did not differ between groups. There was a significant difference in age, with mean age of 62, 66, and 70 in ECOG 0, 1, and 2-4, respectively. Patients (54.6%) remained on therapy for at least 6 months, with no significant difference between groups in ability to complete 6 months of therapy. For ECOG 0, 1, and 2-4, disease control was achieved in 67.2%, 59.6%, and 41.7%, respectively. Analysis of time to death or hospice with a log-rank test showed a significant difference between groups. A multivariate Cox proportional hazards model revealed that patients with ECOG 0 had significantly longer time to death or hospice compared with patients in both other groups after controlling for age, sex, and line of therapy. Conclusion: In this single institution retrospective study of patients receiving nivolumab or pembrolizumab for metastatic cancer, ECOG 0 was associated with disease control and increased time before death or transition to hospice.

Association of Homologous Recombination-DNA Damage Response Gene Mutations with Immune Biomarkers in Gastroesophageal Cancers.

The prevalence of homologous recombination-DNA damage response (HR-DDR) genetic alterations is of therapeutic interest in gastroesophageal cancers. This study is a comprehensive assessment of HR-DDR mutation prevalence across gastroesophageal adenocarcinomas and squamous cell carcinomas. Here we investigate the association of HR-DDR mutations with known predictors for immune-checkpoint inhibition [deficiency in mismatch-repair (dMMRP), tumor mutational burden (TMB), and programmed death ligand 1 (PD-L1)]. We confirmed HR-DDR mutations are present in a subset of gastroesophageal adenocarcinomas (23%) and gastroesophageal squamous cell carcinomas (20%). Biomarker expression of dMMRP (18% vs. 1%) and TMB-high with a cutoff of ≥10 mt/MB (27% vs. 9%) was significantly more prevalent in the DDR-mutated cohort compared with the non-DDR-mutated cohort. Mean combined positive score for PD-L1 in the total adenocarcinoma cohort was significantly higher in the DDR-mutated cohort compared with the non-DDR-mutated cohort (10.1 vs. 5.8). We demonstrated that alterations in ARID1A, BRCA2, PTEN, and ATM are correlated with dMMRP, TMB-high, and increased PD-L1 expression in gastroesophageal adenocarcinomas. Our findings show that a subset of gastroesophageal tumors harbor HR-DDR mutations correlated with established immune biomarkers. By better understanding the relationship between HR-DDR mutations and immune biomarkers, we may be able to develop better immunotherapy combination strategies to target these tumors.

Combination of pan-RAF and MEK inhibitors in NRAS mutant melanoma.

BACKGROUND: Approximately 20% of melanomas contain a mutation in NRAS. However no direct inhibitor of NRAS is available. One of the main signaling pathways downstream of NRAS is the MAPK pathway. In this study we investigated the possibility of blocking oncogenic signaling of NRAS by inhibiting two signaling points in the MAPK pathway. METHODS: Fourteen NRAS mutated human melanoma cell lines were treated with a pan-RAF inhibitor (PRi, Amgen Compd A), a MEK inhibitor (MEKi, trametinib) or their combination and the effects on proliferation, cell cycle progression, apoptosis, transcription profile and signaling of the cells were investigated. RESULTS: The majority of the cell lines showed a significant growth inhibition, with high levels of synergism of the PRi and MEKi combination. Sensitive cell lines showed induction of apoptosis by the combination treatment and there was a correlation between p-MEK levels and synergistic effect of the combination treatment. Proliferation of sensitive cell lines was blocked by the inhibition of the MAPK pathway, which also blocked expression of cyclin D1. However, in resistant cell lines, proliferation was blocked by combined inhibition of the MAPK pathway and cyclin D3, which is not regulated by the MAPK pathway. Resistant cell lines also showed higher levels of p-GSK3ß and less perturbation of the apoptotic profile upon the treatment in comparison with the sensitive cell lines. CONCLUSIONS: The combination of PRi + MEKi can be an effective regimen for blocking proliferation of NRAS mutant melanomas when there is higher activity of the MAPK pathway and dependence of proliferation and survival on this pathway.

Antitumor activity of the ERK inhibitor SCH772984 [corrected] against BRAF mutant, NRAS mutant and wild-type melanoma.

BACKGROUND: In melanoma, dysregulation of the MAPK pathway, usually via BRAF(V600) or NRAS(Q61) somatic mutations, leads to constitutive ERK signaling. While BRAF inhibitors are initially effective for BRAF-mutant melanoma, no FDA-approved targeted therapies exist for BRAF-inhibitor-resistant BRAF(V600), NRAS mutant, or wild-type melanoma. METHODS: The 50% inhibitory concentration (IC50) of SCH772984, a novel inhibitor of ERK1/2, was determined in a panel of 50 melanoma cell lines. Effects on MAPK and AKT signaling by western blotting and cell cycle by flow cytometry were determined. RESULTS: Sensitivity fell into three groups: sensitive, 50% inhibitory concentration (IC50) < 1 µM; intermediately sensitive, IC50 1-2 µM; and resistant, >2 µM. Fifteen of 21 (71%) BRAF mutants, including 4 with innate vemurafenib resistance, were sensitive to SCH772984. All three (100%) BRAF/NRAS double mutants, 11 of 14 (78%) NRAS mutants and 5 of 7 (71%) wild-type melanomas were sensitive. Among BRAF(V600) mutants with in vitro acquired resistance to vemurafenib, those with MAPK pathway reactivation as the mechanism of resistance were sensitive to SCH772984. SCH772984 caused G1 arrest and induced apoptosis. CONCLUSIONS: Combining vemurafenib and SCH722984 in BRAF mutant melanoma was synergistic in a majority of cell lines and significantly delayed the onset of acquired resistance in long term in vitro assays. Therefore, SCH772984 may be clinically applicable as a treatment for non-BRAF mutant melanoma or in BRAF-mutant melanoma with innate or acquired resistance, alone or in combination with BRAF inhibitors.

Effects of MAPK and PI3K pathways on PD-L1 expression in melanoma.

PURPOSE: PD-L1 is the main ligand for the immune inhibitory receptor PD-1. This ligand is frequently expressed by melanoma cells. In this study, we investigated whether PD-L1 expression is controlled by melanoma driver mutations and modified by oncogenic signaling inhibition. EXPERIMENTAL DESIGN: Expression of PD-L1 was investigated in a panel of 51 melanoma cell lines containing different oncogenic mutations, including cell lines with innate and acquired resistance to BRAF inhibitors (BRAFi). The effects of targeted therapy drugs on expression of PD-L1 by melanoma cells were investigated. RESULTS: No association was found between the level of PD-L1 expression and mutations in BRAF, NRAS, PTEN, or amplification of AKT. Resistance to vemurafenib due to the activation of alternative signaling pathways was accompanied with the induction of PD-L1 expression, whereas the resistance due to the reactivation of the MAPK pathway had no effect on PD-L1 expression. In melanoma cell lines, the effects of BRAF, MEK, and PI3K inhibitors on expression of PD-L1 were variable from reduction to induction, particularly in the presence of INFγ. In PD-L1-exposed lymphocytes, vemurafenib paradoxically restored activity of the MAPK pathway and increased the secretion of cytokines. CONCLUSIONS: In melanoma cell lines, including BRAFi-resistant cells, PD-L1 expression is variably regulated by oncogenic signaling pathways. PD-L1-exposed lymphocytes decrease MAPK signaling, which is corrected by exposure to vemurafenib, providing potential benefits of combining this drug with immunotherapies.

Effects of AKT inhibitor therapy in response and resistance to BRAF inhibition in melanoma.

BACKGROUND: The clinical use of BRAF inhibitors for treatment of metastatic melanoma is limited by the development of drug resistance. In this study we investigated whether co-targeting the MAPK and the PI3K-AKT pathway can prevent emergence of resistance or provide additional growth inhibitory effects in vitro. METHODS: Anti-tumor effects of the combination of the BRAF inhibitor (BRAFi) dabrafenib and GSK2141795B (AKTi) in a panel of 23 BRAF mutated melanoma cell lines were evaluated on growth inhibition by an ATP-based luminescent assay, on cell cycle and apoptosis by flow cytometry and on cell signaling by western blot. Moreover, we investigated the possibilities of delaying or reversing resistance or achieving further growth inhibition by combining AKTi with dabrafenib and/or the MEK inhibitor (MEKi) trametinib by using long term cultures. RESULTS: More than 40% of the cell lines, including PTEN-/- and AKT mutants showed sensitivity to AKTi (IC50 < 1.5 µM). The combination of dabrafenib and AKTi synergistically potentiated growth inhibition in the majority of cell lines with IC50 > 5 nM dabrafenib. Combinatorial treatment induced apoptosis only in cell lines sensitive to AKTi. In long term cultures of a PTEN-/- cell line, combinatorial treatment with the MAPK inhibitors, dabrafenib and trametinib, and AKTi markedly delayed the emergence of drug resistance. Moreover, combining AKTi with the MAPK inhibitors from the beginning provided superior growth inhibitory effects compared to addition of AKTi upon development of resistance to MAPK inhibitors in this particular cell line. CONCLUSIONS: AKTi combined with BRAFi-based therapy may benefit patients with tumors harboring BRAF mutations and particularly PTEN deletions or AKT mutations.