Bosutinib in combination with pemetrexed in patients with selected metastatic solid tumors: A phase I study (NCT03023319).

3022 Background: Activation of the Src kinase pathway has been observed in about 50% of cancers of the colon, liver, lung, breast and pancreas. Ceppi, et al, explored that Src inhibitors might be synergistic in combination with pemetrexed. Bosutinib is an approved oral ATP-competitive Bcr-Abl tyrosine-kinase inhibitor with an inhibitory effect on Src kinases. Methods: In this phase 1, dose-escalation study, we enrolled 10 patients with advanced metastatic solid tumors who progressed on standard of care chemotherapy, 9 of whom were evaluable, to receive bosutinib and pemetrexed. Bosutinib was administered once daily in a 3 + 3 dose-escalation study design where the first cohort started at an oral dose of 200 mg daily with I.V. pemetrexed 500 mg/m2 on a three weekly schedule. The primary objective was to determine the dose-limiting toxicity (DLT), and maximum tolerated dose (MTD) of bosutinib with pemetrexed, and the type and frequency of adverse events. Secondary objective(s) were to estimate tumor response rate (RR), progression-free survival (PFS), and overall survival (OS). Results: All patients had progressed on prior chemotherapy and included 9 patients with adenocarcinoma of the lung, and 1 patient with metastatic adenocarcinoma of the appendix. Two patients (22%) had prior pemetrexed exposure. Median age was 62 years (range, 58-44). The median number of bosutinib and pemetrexed cycles received was 2 (range, 1-4). Nine patients were evaluable. The MTD of bosutinib was 300 mg daily in this combination as 2 out of the 3 patients who received 400 mg experienced elevated liver transaminases (>CTCAE Grade 3) and one patient experienced grade 3 fatigue. Two patients (22%) had a partial response, and 6 patients (67%) had stable disease, including 2 patients with prior pemetrexed exposure, and 1 patient had disease progression. The two responders and the subject with the longest stable disease duration demonstrated Src overexpression on immunohistochemical staining of their tumor. Two patients died of sepsis; both had stable disease. Median PFS was 4.1 months (range, 1.2-11.6), and the median OS was 11.9 months (range, 4-36.7). Adverse events included pneumonia/sepsis, diarrhea, fatigue, rash, weakness, transaminitis, hypertension, and thrombocytopenia. Conclusions: The MTD of oral bosutinib was 300 mg daily in combination with pemetrexed 500 mg/m2 every 3 weeks. Despite the limitations of this phase I study there appears potential efficacy of this combination in pretreated patients. We are currently enrolling patients in the expansion cohort. Clinical trial information: NCT03023319.