A phase I trial of combination trastuzumab, lapatinib, and bevacizumab in patients with advanced cancer

Purpose Preclinical data indicate that combination HER2-directed and anti-VEGF therapy may bypass resistance to trastuzumab. A phase I trial was performed to assess safety, activity, and correlates. Experimental design Patients with advanced, refractory malignancy were enrolled (modified 3 + 3 design with expansions for responding tumor types). Patients received lapatinib daily for 21 days, and bevacizumab and trastuzumab every 3 weeks. Correlates included HER2 extracellular domain levels (ECD) and single nucleotide polymorphisms (SNPs). Results Ninety-four patients were treated (median = four prior systemic therapies). The most common related adverse events ≥ grade 2 were diarrhea (n = 33, 35 %) and hypertension (n = 10, 11 %). The recommended phase 2 dose was trastuzumab 6 mg/m2 (loading = 8 mg/m2) and bevacizumab 15 mg/kg every 3 weeks, with lapatinib 1,250 mg daily (full FDA-approved dose of each drug). One patient (1 %) achieved a complete response (CR); eight (9 %), a partial response (PR) (includes breast (n = 7, one of which was HER2 2+ by IHC) and salivary ductal carcinoma (n = 1); and 14 (15 %), stable disease (SD) ≥6 months (total SD ≥ 6 months/PR/CR =23 (25 %). All patients with PR/CR received prior trastuzumab +/− lapatinib. SD ≥ 6 months/PR/CR rate and time to treatment failure (TTF) correlated with elevated baseline HER2 ECD (N = 75 patients tested) but not with HER2 SNPs. Conclusions Combination trastuzumab, lapatinib, and bevacizumab was well-tolerated and demonstrated antitumor activity in heavily pretreated patients with advanced malignancy.