# Sustained Complete Response to Brigatinib in a Young Patient With ALK‐Positive NSCLC Harboring I1171N Mutation Post‐Alectinib Resistance

## TL;DR

A young patient with ALK-positive lung cancer achieved long-term remission with brigatinib after developing resistance to alectinib.

## Contribution

Demonstrates brigatinib's effectiveness against I1171N mutation in ALK-positive NSCLC after alectinib resistance.

## Key findings

- Brigatinib induced a complete and sustained response in a patient with I1171N-mediated alectinib resistance.
- Durable intracranial disease control was observed with brigatinib treatment.
- Repeat molecular testing was critical in identifying the resistance mutation and guiding treatment.

## Abstract

ALK‐rearranged non–small cell lung cancer (NSCLC) represents a paradigm of precision oncology, but acquired resistance to second‐generation ALK tyrosine kinase inhibitors (TKIs) such as alectinib remains inevitable. We report a young, nonsmoker male with ALK‐positive metastatic NSCLC who achieved a sustained complete response (CR) to brigatinib following alectinib resistance mediated by the ALK I1171N mutation. After 22 months of response to alectinib, disease progression prompted repeat molecular profiling, which identified the I1171N alteration. Brigatinib was initiated, and a complete radiologic response was documented within 3 months and has been sustained for over 12 months, including durable intracranial disease control. Sustained CR in I1171N‐mediated alectinib resistance is rare and highlights the critical role of repeat molecular testing to guide ALK TKI sequencing.