Patients with non-small-cell lung cancer (NSCLC) and ALK rearrangements generally have a progression-free survival of 8-11 months while on treatment with the ALK inhibitor crizotinib. However, resistance inevitably develops, with the brain a common site of progression. More potent ALK inhibitors with consistently demonstrable CNS activity and good tolerability are needed urgently. Alectinib is a novel, highly selective, and potent ALK inhibitor that has shown clinical activity in patients with crizotinib-naive ALK-rearranged NSCLC. We did a phase 1/2 study of alectinib to establish the recommended phase 2 dose of the drug and examine its activity in patients resistant or intolerant to crizotinib.

We enrolled patients with ALK-rearranged NSCLC who progressed on or were intolerant to crizotinib. We administered various oral doses of alectinib (300-900 mg twice a day) during the dose-escalation portion of the study (phase 1), to ascertain the recommended dose for phase 2. We used Response Evaluation Criteria in Solid Tumors criteria (version 1.1) to investigate the activity of alectinib in all patients with a baseline scan and at least one post-treatment scan (CT or MRI), with central radiological review of individuals with brain metastases. We assessed safety in all patients who received at least one dose of alectinib. Here, we present data for the phase 1 portion of the study, the primary objective of which was to establish the recommended phase 2 dose; phase 2 is ongoing. This trial is registered at ClinicalTrials.gov, number NCT01588028.

47 patients were enrolled. Alectinib was well tolerated, with the most common adverse events being fatigue (14 [30%]; all grade 1-2), myalgia (eight [17%]; all grade 1-2), and peripheral oedema (seven [15%] grade 1-2, one [2%] grade 3). Dose-limiting toxic effects were recorded in two patients in the cohort receiving alectinib 900 mg twice a day; one individual had grade 3 headache and the other had grade 3 neutropenia. The most common grade 3-4 adverse events were increased levels of γ-glutamyl transpeptidase (two [4%]), a reduction in the number of neutrophils (two [4%]), and hypophosphataemia (two [4%]). Three patients reported four grade 4 serious adverse events that were deemed unrelated to alectinib: acute renal failure; pleural effusion and pericardial effusion; and brain metastasis. At data cut-off (median follow-up 126 days [IQR 84-217]), 44 patients could be assessed for activity. Investigator-assessed objective responses were noted in 24 (55%) patients, with a confirmed complete response in one (2%), a confirmed partial response in 14 (32%), and an unconfirmed partial response in nine (20%). 16 (36%) patients had stable disease; the remaining four (9%) had progressive disease. Of 21 patients with CNS metastases at baseline, 11 (52%) had an objective response; six (29%) had a complete response (three unconfirmed) and five (24%) had a partial response (one unconfirmed); eight (38%) patients had stable disease and the remaining two (10%) had progressive disease. Pharmacokinetic data indicated that mean exposure (AUC0-10) after multiple doses of alectinib (300-600 mg twice a day) was dose-dependent.

Alectinib was well tolerated, with promising antitumour activity in patients with ALK-rearranged NSCLC resistant to crizotinib, including those with CNS metastases. On the basis of activity, tolerability, and pharmacokinetic data, we chose alectinib 600 mg twice a day as the recommended dose for phase 2.

Chugai Pharmaceuticals, F Hoffmann La-Roche.