Zurletrectinib is a next-generation TRK inhibitor with strong intracranial activity against NTRK fusion-positive tumours with on-target resistance to first-generation agents.

BACKGROUND: While NTRK fusion-positive cancers can be exquisitely sensitive to first-generation TRK inhibitors, resistance inevitably occurs, mediated in many cases by acquired NTRK mutations. Next-generation inhibitors (e.g., selitrectinib, repotrectinib) maintain activity against these TRK mutant tumors; however, there are no next-generation TRK inhibitors approved by the FDA and select trials have stopped treating patients. Thus, the identification of novel, potent and specific next-generation TRK inhibitors is a high priority. METHODS: In silico modeling and in vitro kinase assays were performed on TRK wild type (WT) and TRK mutant kinases. Cell viability and clonogenic assays as well as western blots were performed on human primary and murine engineered NTRK fusion-positive TRK WT and mutant cell models. Finally, zurletrectinib was tested in vivo in human xenografts and murine orthotopic glioma models harboring TRK-resistant mutations. RESULTS: In vitro kinase and in cell-based assays showed that zurletrectinib, while displaying similar potency against TRKA, TRKB, and TRKC WT kinases, was more active than other FDA approved or clinically tested 1st- (larotrectinib) and next-generation (selitrectinib and repotrectinib) TRK inhibitors against most TRK inhibitor resistance mutations (13 out of 18). Similarly, zurletrectinib inhibited tumor growth in vivo in sub-cute xenograft models derived from NTRK fusion-positive cells at a dose 30 times lower when compared to selitrectinib. Computational modeling suggests this stronger activity to be the consequence of augmented binding affinity of zurletrectinib for TRK kinases. When compared to selitrectinib and repotrectinib, zurletrectinib showed increased brain penetration in rats 0.5 and 2 h following a single oral administration. Consistently, zurletrectinib significantly improved the survival of mice harboring orthotopic NTRK fusion-positive, TRK-mutant gliomas (median survival = 41.5, 66.5, and 104 days for selitrectinib, repotrectinib, and zurletrectinib respectively; P < 0.05). CONCLUSION: Our data identifies zurletrectinib as a novel, highly potent next-generation TRK inhibitor with stronger in vivo brain penetration and intracranial activity than other next-generation agents.

Mutations in the Serine/Threonine Kinase BRAF: Oncogenic Drivers in Solid Tumors.

Since their discovery in 2002, BRAF mutations have been identified as clear drivers of oncogenesis in several cancer types. Currently, their incidence rate is nearly 7% of all solid tumors with BRAF V600E constituting approximately 90% of these diagnoses. In melanoma, thyroid cancer, and histiocytic neoplasms, BRAF hotspot mutations are found at a rate of about 50%, while in lung and colorectal cancers they range from 3% to 10% of reported cases. Though present in other malignancies such as breast and ovarian cancers, they constitute a small portion of diagnoses (<1%). Given their frequency along with advancements in screening technologies, various methods are used for the detection of BRAF-mutant cancers. Among these are targeted next-generation sequencing (NGS) on tumor tissue or circulating tumor DNA (ctDNA) and immunohistochemistry (IHC)-based assays. With advancements in detection technologies, several approaches to the treatment of BRAF-mutant cancers have been taken. In this review, we retrace the milestones that led to the clinical development of targeted therapies currently available for these tumors.

Injectable Nanocomposite Hydrogels Improve Intraperitoneal Co-delivery of Chemotherapeutics and Immune Checkpoint Inhibitors for Enhanced Peritoneal Metastasis Therapy.

Intraperitoneal co-delivery of chemotherapeutic drugs (CDs) and immune checkpoint inhibitors (ICIs) brings hope to improve treatment outcomes in patients with peritoneal metastasis from ovarian cancer (OC). However, current intraperitoneal drug delivery systems face issues such as rapid drug clearance from lymphatic drainage, heterogeneous drug distribution, and uncontrolled release of therapeutic agents into the peritoneal cavity. Herein, we developed an injectable nanohydrogel by combining carboxymethyl chitosan (CMCS) with bioadhesive nanoparticles (BNPs) based on polylactic acid-hyperbranched polyglycerol. This system enables the codelivery of CD and ICI into the intraperitoneal space to extend drug retention. The nanohydrogel is formed by cross-linking of aldehyde groups on BNPs with amine groups on CMCS via reversible Schiff base bonds, with CD and ICI loaded separately into BNPs and CMCS network. BNP/CMCS nanohydrogel maintained the activity of the biomolecules and released drugs in a sustained manner over a 7 day period. The adhesive property, through the formation of Schiff bases with peritoneal tissues, confers BNPs with an extended residence time in the peritoneal cavity after being released from the nanohydrogel. In a mouse model, BNP/CMCS nanohydrogel loaded with paclitaxel (PTX) and anti-PD-1 antibodies (αPD-1) significantly suppressed peritoneal metastasis of OC compared to all other tested groups. In addition, no systemic toxicity of nanohydrogel-loaded PTX and αPD-1 was observed during the treatment, which supports potential translational applications of this delivery system.