ABSTRACT
The efficacy of the highly selective RET inhibitor selpercatinib is now established in RET-driven cancers, and we sought to characterize the molecular determinants of response and resistance. We find that the pre-treatment genomic landscape does not shape the variability of treatment response except for rare instances of RAS-mediated primary resistance. By contrast, acquired selpercatinib resistance is driven by MAPK pathway reactivation by one of two distinct routes. In some patients, on- and off-target pathway reactivation via secondary RET solvent front mutations or MET amplifications are evident. In other patients, rare RET-wildtype tumor cell populations driven by an alternative mitogenic driver are selected for by treatment. Multiple distinct mechanisms are often observed in the same patient, suggesting polyclonal resistance may be common. Consequently, sequential RET-directed therapy may require combination treatment with inhibitors targeting alternative MAPK effectors, emphasizing the need for prospective characterization of selpercatinib-treated tumors at the time of monotherapy progression.
Subject(s)
Lung Neoplasms , Thyroid Neoplasms , Humans , Lung , Lung Neoplasms/drug therapy , Lung Neoplasms/genetics , Mutation , Prospective Studies , Proto-Oncogene Proteins c-ret/genetics , Thyroid Neoplasms/drug therapy , Thyroid Neoplasms/geneticsABSTRACT
HER2 mutations define a subset of metastatic breast cancers with a unique mechanism of oncogenic addiction to HER2 signaling. We explored activity of the irreversible pan-HER kinase inhibitor neratinib, alone or with fulvestrant, in 81 patients with HER2-mutant metastatic breast cancer. Overall response rate was similar with or without estrogen receptor (ER) blockade. By comparison, progression-free survival and duration of response appeared longer in ER+ patients receiving combination therapy, although the study was not designed for direct comparison. Preexistent concurrent activating HER2 or HER3 alterations were associated with poor treatment outcome. Similarly, acquisition of multiple HER2-activating events, as well as gatekeeper alterations, were observed at disease progression in a high proportion of patients deriving clinical benefit from neratinib. Collectively, these data define HER2 mutations as a therapeutic target in breast cancer and suggest that coexistence of additional HER signaling alterations may promote both de novo and acquired resistance to neratinib. SIGNIFICANCE: HER2 mutations define a targetable breast cancer subset, although sensitivity to irreversible HER kinase inhibition appears to be modified by the presence of concurrent activating genomic events in the pathway. These findings have implications for potential future combinatorial approaches and broader therapeutic development for this genomically defined subset of breast cancer.This article is highlighted in the In This Issue feature, p. 161.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Breast Neoplasms, Male/drug therapy , Breast Neoplasms/drug therapy , Receptor, ErbB-2/antagonists & inhibitors , Receptors, Estrogen/antagonists & inhibitors , Adult , Aged , Aged, 80 and over , Antineoplastic Combined Chemotherapy Protocols/pharmacology , Breast Neoplasms/genetics , Breast Neoplasms/pathology , Breast Neoplasms, Male/genetics , Breast Neoplasms, Male/pathology , Cell Line, Tumor , DNA Mutational Analysis , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/genetics , Drug Synergism , Estrogen Receptor Antagonists/pharmacology , Estrogen Receptor Antagonists/therapeutic use , Female , Fulvestrant/pharmacology , Fulvestrant/therapeutic use , Humans , Male , Middle Aged , Mutation , Prospective Studies , Protein Kinase Inhibitors/pharmacology , Protein Kinase Inhibitors/therapeutic use , Quinolines/pharmacology , Quinolines/therapeutic use , Receptor, ErbB-2/genetics , Receptor, ErbB-2/metabolism , Receptors, Estrogen/metabolism , Signal Transduction/drug effects , Signal Transduction/genetics , Treatment OutcomeABSTRACT
BACKGROUND: PI3K pathway activation is common in endometrial cancer. We evaluated the safety and efficacy of the dual PI3K/mTOR inhibitor, LY3023414, in patients with advanced endometrial cancer harboring activating mutations in the PI3K pathway. METHODS: We conducted a single-arm phase 2 study of monotherapy LY3023414. Eligible patients had advanced endometrial cancer of any grade, prior management with 1-4 cytotoxic lines, and PI3K pathway activation prospectively defined as a loss-of-function PTEN alteration or activating alteration in PIK3CA, AKT1, PIK3R1, PIK3R2, or MTOR. The primary objective was best overall response rate (ORR) per RECIST 1.1. RESULTS: Twenty-eight patients were treated; histologies included endometroid (39%), carcinosarcoma (25%), serous (21%), and mixed (14%). Patients were heavily pretreated, with a median of 2 prior cytotoxic lines (range, 1-3). The most common alterations involved PIK3CA (68%), PTEN (43%), and PIK3R1 (32%). In the 25 efficacy-evaluable patients, the ORR was 16% (90% CI, 7%-100%), and the clinical benefit rate was 28% (90% CI, 16%-100%). Four patients had a confirmed partial response, and 2 responses lasted for >9 months. The median progression-free survival and overall survival were 2.5 months (95% CI, 1.2-3.0) and 9.2 months (95% CI, 5.0-15.9), respectively. The most common all-grade treatment-related adverse events were anemia (71%), hyperglycemia (71%), hypoalbuminemia (68%), and hypophosphatemia (61%). No correlation between molecular alterations and response was observed. CONCLUSION: In patients with heavily pretreated advanced endometrial cancer prospectively selected for tumors with activating PI3K pathway mutations, LY3023414 demonstrated modest single-agent activity and a manageable safety profile.
