BTK C481S

PCA and FEL results further revealed the dynamic variations caused by these mutations. These findings underline the significant impact of mutations T474M and C481S on the binding free energy, highlighting the importance of these residues in ibrutinib-BTK interactions.

This study highlights the complex clonal dynamics of BTK mutations in R/R CLL patients undergoing pirtobrutinib treatment, and the extent of resistance without an obvious genomic driver. NCT03740529.

BTK inhibitors (BTKis) such as ibrutinib (as monotherapy or combined with R-CHOP/R-DHAP), acalabrutinib (with rituximab and bendamustine), and pirtobrutinib have significantly improved outcomes of relapsed/refractory disease. In parallel, biomarker-driven approaches and precision-medicine strategies are emerging to personalize disease monitoring and treatment selection. Collectively, these developments underscore the evolving role of BTK inhibition within broader immune-based and targeted treatment paradigms in MCL.

The first-generation BTKi ibrutinib demonstrated significant efficacy, leading to the development of second-generation agents (acalabrutinib, zanubrutinib) with improved selectivity and safety...Noncovalent BTKis, such as pirtobrutinib, offer effective options for patients relapsing after covalent BTKi therapy...Future clinical trials are expected to adopt mutation-driven stratification to guide therapeutic sequencing. Ultimately, overcoming BTKi resistance will require innovative strategies, including BTK degraders, bispecific antibodies, and T cell-engaging immunotherapies.

Ex vivo pharmacologic profiling suggested that during pirtobrutinib therapy, peripheral blood mononuclear cells (CLL cells) became resensitized to ibrutinib and other targeted agents. Combination therapy, including ibrutinib and venetoclax, was effective regardless of genomic background and even after relapse from pirtobrutinib monotherapy.

In summary, our comprehensive multiomics analysis of CLL patients undergoing ibrutinib therapy has unveiled early immunomodulatory effects on T cells and adaptative mechanisms in CLL cells. These findings can contribute to the identification of resistance mechanisms and the discovery of novel therapeutic targets.

Based on noncovalent inhibitor ARQ-531, we previously developed two potent BTK PROTACs 6e and SC-3e, which exhibited poor pharmacokinetic property...Furthermore, compound 27 displayed excellent cell antiproliferative activities, metabolic stability in mouse liver microsomes and improved bioavailability in mice. Overall, 27 is a highly effective and selective BTK degrader that is suitable for in vivo efficacy investigations.

While BTK inhibitors (BTKi), such as ibrutinib, have been effective, resistance-both intrinsic and acquired-poses a significant challenge, often associated with BTK mutations like C481S...Agents such as NRX-0492, BGB-16673, NX-5948, NX-2127, HZ-Q1060, ABBV-101, and AC676 have shown significant BTK degradation in preclinical and early clinical trials...These BTK degraders have demonstrated favorable safety profiles, with manageable adverse events, and offer a novel therapeutic avenue for patients with BTKi-resistant malignancies. As clinical trials progress, these degraders hold the potential to significantly enhance treatment outcomes, offering a new frontier in personalized cancer therapy.

We here overcame these challenges by multiplexing digital PCR (mdPCR) in three assays that can cover 96% of ibrutinib-resistant cases...We found mdPCR to bemore sensitive than NGS, particularly at low allelic frequencies, making it more suitable for the detection and quantification of small mutated clones. Thus, mdPCR offers high sensitivity, is expected to be more rapid and cost-effective than NGS in detecting resistance mutations to improve the therapeutic choice at relapse after exposure to BTK inhibitors.

The first-in-class covalent BTK inhibitor, Ibrutinib, binds to the C481 amino acid residue to block the BTK enzyme and prevent the downstream signaling...To bypass the C481S mutation, non-covalent BTKi, such as Pirtobrutinib, were developed and are active against both wild-type and the C481S mutation...In addition, we discuss the new emerging class of BTK degraders, which utilize the evolution of proteolysis-targeting chimeras (PROTACs) to degrade the BTK protein and constitute an important avenue of overcoming resistance. The moving landscape of resistance to BTKi and the development of new therapeutic strategies highlight the ongoing advances being made towards the pursuit of a cure for B-cell lymphoid malignancies.

One acalabrutinib-treated patient and 4 ibrutinib-treated patients had emergent BTK/PLCG2 co-mutations. While common BTK C481 mutations were observed with both treatments, patterns of mutation and co-mutation frequency, mutation VAF, and uncommon BTK variants varied with acalabrutinib (T474I and E41V) and ibrutinib (L528W, A428D) in this patient population.

Collectively our findings suggest that phosphorylation of Y223 serves as a useful proxy for phosphorylation of phospholipase C2 (PLCG2), the endogenous substrate of BTK. However, in contrast to a frequently held conception, this post-translational modification is dispensable for the function of BTK.