ALEX CNS Analysis

Background

The ALEX CNS analysis was a prespecified subgroup and sensitivity analysis from ALEX, a phase III randomized open-label trial comparing alectinib (a next-generation ALK inhibitor with superior CNS penetration) versus crizotinib (first-generation ALK inhibitor, limited CNS penetration) in treatment-naive ALK-positive NSCLC. Brain metastases occur in ~30–50% of ALK+ NSCLC patients and represent the predominant site of failure with crizotinib. The CNS analysis was designed to quantify alectinib's intracranial activity and establish it as the superior treatment for ALK+ NSCLC patients with brain metastases.

Interventions and follow up

Arm A: Alectinib 600 mg PO BID
Arm B: Crizotinib 250 mg PO BID
Primary endpoint: ALEX primary: investigator-assessed PFS; CNS analysis primary: time to CNS progression (CNS PFS) in patients with/without baseline BM; secondary: intracranial ORR, CNS complete response rate, duration of CNS response
mFollow up: 27.8 months (ALEX primary analysis)

Results

With baseline BM — 12-mo CNS PFS: alectinib 82.9% vs crizotinib 62.5%, HR 0.40, 95% CI 0.25–0.64
With baseline BM — intracranial ORR (measurable CNS lesions): alectinib 81% vs crizotinib 50%, P<.001
With baseline BM — CNS CR: alectinib 38% vs crizotinib 7%
Without baseline BM — 12-mo CNS PFS: alectinib 96% vs crizotinib 77%, HR 0.16, 95% CI 0.07–0.39
Overall ALEX mPFS: 34.8 vs 10.9 months, HR 0.43, P<.0001

Adverse events

Grade ≥3 AEs: alectinib 41% vs crizotinib 50%
CNS AEs (seizures, altered cognition): alectinib 3.9% vs crizotinib 5.3%
Grade ≥3 ALT/AST elevation: alectinib 4.6% vs crizotinib 5.3%
Creatine phosphokinase elevation (alectinib) Grade ≥3: 4.6%
Edema: alectinib 9.9% vs crizotinib 12.6%
Other: GI toxicity lower with alectinib; photosensitivity alectinib-specific (all grades 9.9%)

Conclusions

Alectinib achieved dramatically superior CNS activity versus crizotinib in ALK+ NSCLC with brain metastases — 81% intracranial ORR (vs 50%), 38% CNS CR (vs 7%), and 60% reduction in CNS progression risk (HR 0.40) — establishing alectinib as the standard of care for ALK+ NSCLC with brain metastases and demonstrating that CNS penetration of the systemic ALK inhibitor is a critical determinant of intracranial disease control.

Key Limitations

CNS analysis is a prespecified subgroup of ALEX, not a standalone primary endpoint trial — statistical power for CNS-specific comparisons is limited by subgroup size; BM diagnosis by local MRI (not standardized central review for BM); CNS ORR and PFS are composite endpoints subject to measurement variability; ALEX was not designed specifically for a BM-enriched population; alectinib's superiority is driven by both superior systemic activity (mPFS 34.8 vs 10.9 months) and CNS penetration — difficult to isolate CNS-specific benefit; lorlatinib (3rd-generation ALK inhibitor) subsequently showed superior CNS activity vs crizotinib in CROWN; acquired resistance to alectinib via ALK G1202R mutation has CNS implications; SRS role concurrent with next-gen ALKi is evolving.

Clinical Context

ALEX established alectinib as a CNS-active first-line ALK inhibitor, and it was FDA-approved for 1L ALK+ NSCLC in 2017. The subsequent CROWN trial (lorlatinib vs crizotinib, NEJM 2020) demonstrated lorlatinib's superior CNS activity vs crizotinib, leading to its preferred positioning for ALK+ NSCLC with BM. Per ASCO/ESMO, both alectinib and lorlatinib are recommended first-line options for ALK+ NSCLC. The standard approach for ALK+ NSCLC with BM is a first-line next-generation ALK inhibitor (lorlatinib or alectinib) with deferral of SRS/WBRT unless symptomatic or large lesions require urgent local therapy. The dramatic intracranial ORR with next-gen ALKi has transformed management of ALK+ NSCLC BM from urgent brain RT toward systemic therapy-first approaches.

References