Pyrotinib, an irreversible pan-HER receptor tyrosine kinase inhibitor, showed promising safety and efficacy in a phase 2 trial of 15 adults with HER2-mutant non–small cell lung cancer and also topped afatinib in in vitro and murine studies, investigators reported.
In the phase 2 trial, objective response rate was 53%, a median overall survival was 12.9 months, and median progression-free survival was 6.4 months, wrote Yan Wang of Tongji University, Shanghai, China, together with associates. Pyrotinib showed superior antitumor activity, compared with afatinib, in a patient-derived organoid (P = .004) and xenograft mouse model (P = .0471), they reported in Annals of Oncology.
About 2% to 3% of patients with non–small cell lung cancer (NSCLC) have HER2 mutations, which most often involve an exon 20 insertion. Because HER2-targeting agents such as afatinib, dacomitinib, neratinib, and trastuzumab have limited activity against these cancers, patients usually receive chemotherapy, even though it is less effective than in lung cancers with ALK or ROS1 rearrangements.
To seek a better treatment option, the researchers created a HER2YVMA insertion patient-derived organoid model and a patient-derived xenograft mouse model, both of which confirmed the superior antitumor activity of pyrotinib, compared with afatinib or T-DM1 (ado-trastuzumab emtansine). For example, tumor burdens in mice fell by an average of 52% with pyrotinib but rose by 25% on afatinib and by 11% on T-DM1.
Accordingly, the researchers conducted a phase 2 trial of oral pyrotinib (400 mg daily) in 15 adults with NSCLC characterized by HER2 mutations in exon 20 or exon 19, the tyrosine kinase domain. Patients had an Eastern Cooperative Oncology Group performance status of 0-2, lacked symptomatic brain metastases, and had progressed on standard therapy.
In all, nine patients (60%) developed adverse events, the most common of which were grade 1 or 2 diarrhea, decreased hemoglobin levels, and hypocalcemia. There were no grade 3 or 4 events. Progression-free survival ranged from 1.7 to 23.4 months and one-third of patients stayed on pyrotinib for more than 1 year. Among two patients with asymptomatic brain metastases, one stopped pyrotinib at 4 weeks because of primary tumor progression but the other achieved stable disease on treatment. Three (23%) patients developed incident brain metastases on pyrotinib. The sole patient who progressed on a prior HER2-targeted therapy (afatinib) responded to pyrotinib.
Taken together, these findings support further study of pyrotinib in patients with NSCLC with HER2 exon 20 mutations, the researchers wrote. They have initiated a multicenter, phase 2 trial, which is currently in progress.
Funders included the National Natural Science Foundation of China, the “Shuguang Program” supported by Shanghai Education Development Foundation and Shanghai Municipal Education Commission, the Science and Technology Commission of Shanghai Municipality, the Development Fund for Shanghai Talents, the University of Iowa Start-up Funds, and the American Cancer Society. The investigators reported having no conflicts of interest.
SOURCE: Wang Y et al. Ann Oncol. 2018 Dec 31. doi: 10.1093/annonc/mdy542.