To establish the safety of escalating doses of MM-121 in combination with erlotinib in order to determine the recommended phase 2 dose of the combination for the second part of the study. Dose-escalation conducted using standard 3+3 model to determine maximum tolerated dose. Reports of Dose-Limiting Toxicities (DLTs) were assessed to determine the MTD.

Using a 3+3 dose escalation model, the maximum tolerated dose was determined by assessing dose-limiting toxicities in each cohort. If 3 patients were treated and passed the observation window, escalation to the next cohort was initiated. If a DLT was reported, 3-4 additional patients were enrolled and observed. If a DLT was observed in the expanded cohort, this dose was considered to be the maximum tolerated dose. The maximum tolerated dose was defined at the cohort in which two dose-limiting toxicities were observed, or as the highest target dose tested in the absence of DLTs.

The determined MTD was used as the recommended Phase 2 dose.

All participants treated in the Phase 1 dose-escalation portion of the study

This was a time-to-event measure using Progression-Free Survival (PFS) comparing MM-121 + erlotinib vs.erlotinib alone. Progression of disease is defined using Response Evaluation Criteria In Solid Tumors Criteria (RECIST v1.1), as a 20% increase in the sum of the longest diameter of target lesions, or a measurable increase in a non-target lesion, or the appearance of new lesions". Progression free survival was defined as the number of weeks from the date of randomization to the date of death or progression. If neither death nor progression was observed during the study, PFS data was censored at the last non-progressive disease valid tumor assessment unless the patient was discontinued due to symptomatic deterioration. If this occurred, the patient was counted as having progressive disease (PD).

Tumor tissue samples were obtained from patients prior to enrollment. Samples were analyzed using RNA-ISH for the expression of the biomarker, heregulin. Progression-free survival was assessed using RECIST v 1.1 to determine whether patients whose tumors express HRG have a lower PFS than those whose tumors do not express HRG, and to assess whether the addition of MM-121 to erlotinib can increase PFS in HRG-high patients.

Patients with available tissue for heregulin testing