A Phase Ii Study Of Lorlatinib In Patients (Pts) With Alk-Positive (Alk Plus ) Lung Cancer With Brain-Only Progression.

9595 Background: Lorlatinib is a 3rd-generation ALK tyrosine kinase inhibitor (TKI) developed to penetrate the central nervous system (CNS) and overcome resistance to 2nd-generation (2nd-gen) ALK TKIs. In a phase II study, lorlatinib demonstrated significant intracranial (IC) activity after failure of 2nd-gen TKIs. As treatment discontinuation for extracranial (EC) progression can confound assessment of durability of IC response, we performed a phase II study (NCT02927340) to selectively evaluate lorlatinib activity in ALK+ pts with CNS-only disease. Methods: Between 11/2016 and 1/2019, 22 pts with IC progression on an ALK TKI with no other sites of measurable disease were enrolled at 2 institutions. Pts received lorlatinib at a starting dose of 100 mg QD. The primary endpoint was the IC disease control rate (DCR) at 12 weeks per modified RECIST v1.1. Secondary endpoints were IC objective response rate (ORR), duration of response (DOR), and progression-free survival (PFS). Results: Of the 22 pts enrolled, 21 (95%) had progressed on a 2nd-gen ALK TKI and 14 (64%) had previously received CNS radiation (median 21.1 months between radiation and lorlatinib). Median number of prior ALK TKIs was 2 (range 1-4). As of the data cutoff of 12/15/19, median follow-up was 14 months. At 12 weeks, the IC-DCR was 95%, including 8 pts with stable disease. Best IC ORR was 59% with 6 complete and 7 partial responses. Nine (41%) pts relapsed on study, including 3 IC-only, 5 EC-only, and 1 combined relapse. Four pts continued treatment beyond EC-only progression. Although median IC DOR and PFS were not estimable due to few progression events, the IC progression-free rate at 12 months was 81% (95% CI: 53%-94%). Twelve pts have discontinued study treatment due to progression (n = 6), edema (n = 1), pulmonary hypertension (n = 1), or transition to commercial lorlatinib (n = 4). Conclusions: Lorlatinib induces durable intracranial responses in pts with CNS-only progression on 2nd-gen ALK TKIs, suggesting that CNS-specific relapses are primarily driven by ALK-dependent mechanisms. Further studies are needed to characterize the molecular basis of sensitivity to lorlatinib in this unique subgroup of pts with ALK+ lung cancer. Clinical trial information: NCT02927340 .