73P - Combined cellular and biochemical profiling of BTK inhibitor nemtabrutinib reveals potential application in MAPK pathway-driven cancers

Background

Nemtabrutinib is a reversible inhibitor of both wild-type Bruton’s tyrosine kinase (BTK) and BTK mutants associated with acquired resistance against irreversible BTK inhibitors, such as ibrutinib. To identify differentiators from other BTK inhibitors and potential novel therapeutic applications, nemtabrutinib was profiled on a panel of 160 human cancer cell line viability assays. Bioinformatic analyses were performed to identify drug response biomarkers and to identify potential cross-reactivities.

Methods

Cancer cell line viability assays were carried out using ATP Lite (Revvity). Half-maximal inhibitory concentration (IC₅₀) values were used for bioinformatic analyses. Kinase selectivity was determined by profiling at 1 μmol/L on a 255 wild-type kinases in mobility shift assays at Carna Biosciences (Japan), followed by IC₅₀ determination on individual kinases.

Results

Genomic biomarker analysis of nemtabrutinib’s IC₅₀ profile in 160 cell lines revealed BRAF mutation status as significantly predictive of drug response, with BRAF-mutant cell lines being three times more sensitive than BRAF wild-type cell lines. Consistent with this, the IC₅₀ profile of nemtabrutinib on 102 of the 160 cell lines was most similar to (B)RAF, MEK and ERK inhibitors (Pearson correlation > 0.5) but differed from marketed BTK inhibitors. Furthermore, cell line response correlated with basal FGFR3 expression levels and genetic dependency on several mitogen-activated protein kinase (MAPK) genes. Biochemical kinase profiling confirmed that nemtabrutinib inhibits MEK1 and several growth factor receptor kinases, including FGFR3. Surface plasmon resonance binding experiments showed strong binding to MEK1 but not to B-RAF, which confirmed that nemtabrutinib’s preferential targeting of MAPK pathway-driven cell lines is due to cross-reactivity with MEK1.

Conclusions

Combined cancer cell panel and biochemical profiling revealed previously underappreciated cross-reactivities of nemtabrutinib that may be explored for therapeutic application besides B-cell cancers.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Oncolines B.V.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.