ROS1 fusion (ROS1-positive)

aka ROS1 fusion, ROS1 rearrangement, ROS1-positive, ROS1+, CD74-ROS1, CD74::ROS1

A ROS1 fusion drives about 1 to 2 percent of lung adenocarcinomas and behaves much like ALK. Crizotinib, entrectinib, repotrectinib and taletrectinib are approved for it.

ROS1 rearrangements (partners include CD74, SLC34A2 and EZR) are detected by FISH, IHC or sequencing; the FDA list carries the Oncomine Dx Target Test for crizotinib and FoundationOne CDx and Liquid CDx for entrectinib. Crizotinib was the first drug labelled for ROS1-positive metastatic NSCLC (2016); entrectinib (2019) and repotrectinib (2023) followed, the latter with activity after prior ROS1 inhibitors and against the G2032R solvent-front mutation; taletrectinib (Ibtrozi, 2025) is labelled for locally advanced or metastatic ROS1-positive NSCLC without a named test requirement.

Part ofROS1· ROS1 All readouts

ROS1: what it is and how drugs act on it · animated schematic, not to scale

Target · the protein and the cell it sits on
Drug · antibody, small molecule, cell or radioligand
Effect · signal, damage or kill

In plain words · A gene fusion in about 1-2% of lung cancers that responds for years to targeted pills, now in their third generation.

Sequencing 4 approval thresholds

What it means for a patient

A ROS1 fusion means a ROS1 tablet (repotrectinib, taletrectinib, entrectinib or crizotinib) is the first treatment for advanced lung cancer, with the newer drugs preferred where brain spread is a concern. If the tumour later grows, a second ROS1 inhibitor may still work depending on the resistance mutation found.

Written only from the label or guideline text cited on this page. Not medical advice; your own report and the reading your team gives it come first.

Scoring rule

A ROS1 gene fusion or rearrangement by FISH, immunohistochemistry confirmed by a molecular method, or DNA or RNA sequencing of tissue or plasma.

“ROS1 fusions”
FDA: List of FDA-Authorized Companion Diagnostic Devices

Thresholds used in approvals

Threshold	Drug	Cancer	Regulator	Source
ROS1-positive	Entrectinib	Non-small-cell lung cancer	FDA	label
ROS1-positive	Repotrectinib	Non-small-cell lung cancer	FDA	label
ROS1-positive	Taletrectinib	Non-small-cell lung cancer	FDA	label
ALK or ROS1-positive	Crizotinib	Non-small-cell lung cancer	FDA	label

Drugs whose label names it

Entrectinib Repotrectinib Taletrectinib Crizotinib

Companion diagnostics (FDA list)

Device	Maker	Indication and sample	Drug	PMA / 510(k)
Oncomine Dx Target Test	Life Technologies (Thermo Fisher Scientific)	Non-Small Cell Lung Cancer (NSCLC) - Tissue	Crizotinib	P160045 (06/22/2017)
FoundationOne CDx	Foundation Medicine	Non-Small Cell Lung Cancer (NSCLC) - Tissue	Entrectinib	P170019/S014 (06/07/2022)
FoundationOne Liquid CDx	Foundation Medicine	Non-Small Cell Lung Cancer (NSCLC) - Plasma	Entrectinib	P190032/S004 (12/22/2022)

Tests that measure it

FoundationOne CDx FoundationOne Liquid CDx Oncomine Dx Target Test Tempus xT and xT CDx FoundationOne CDx FoundationOne Liquid CDx Guardant360 CDx Illumina TruSight Oncology Comprehensive

Trials that name this readout

Matched on the name and aliases of the readout in the title, setting and summary of each trial; a match is a mention, not proof the readout was an entry criterion.