Discovery of 9H-pyrimido[4,5-b]indole derivatives as dual RET/TRKA inhibitors.

Aberrant RET kinase signaling is activated in numerous cancers including lung, thyroid, breast, pancreatic, and prostate. Recent approvals of selective RET inhibitors, pralsetinib and selpercatinib, has shifted the focus of RET kinase drug discovery programs towards the development of selective inhibitors. However, selective inhibitors invariably lose efficacy as the selective nature of the inhibitor places Darwinian-like pressure on the tumor to bypass treatment through the selection of novel oncogenic drivers. Further, selective inhibitors are restricted for use in tumors with specific genetic backgrounds that do not encompass diverse patient classes. Here we report the identification of a pyrimido indole RET inhibitor found to also have activity against TRK. This selective dual RET/TRK inhibitor can be utilized in tumors with both RET and TRK genetic backgrounds and can also provide blockade of NTRK-fusions that are selected for from RET inhibitor treatments. Efforts towards developing dual RET/TRK inhibitors can be beneficial in terms of encompassing more diverse patient classes while also achieving blockade against emerging resistance mechanisms.

Kinase inhibitor macrocycles: a perspective on limiting conformational flexibility when targeting the kinome with small molecules.

Methods utilized for drug discovery and development within the kinome have rapidly evolved since the approval of imatinib, the first small molecule kinase inhibitor. Macrocycles have received increasing interest as a technique to improve kinase inhibitor drug properties evident by the FDA approvals of lorlatinib, pacritinib, and repotrectinib. Compared to their acyclic counterparts, macrocycles can possess improved pharmacodynamic and pharmacokinetic properties. This review highlights clinical success stories when implementing macrocycles in kinase-based drug discovery and showcases that macrocyclization is a clinically validated drug discovery strategy when targeting the kinome.

Design and Synthesis of Orally Active Quinolyl Pyrazinamides as Sigma 2 Receptor Ligands for the Treatment of Pancreatic Cancer.

Sigma 2 receptor (σ2R) is overexpressed in select cancers and is regarded as a biomarker for tumor proliferation. σ2R ligands are emerging as promising theranostics for cancer and neurodegenerative diseases. Herein, we describe the design and synthesis of a series of novel quinolyl pyrazinamides as selective and potent σ2R ligands that show sub-micromolar potency in pancreatic cancer cell lines. Compounds 14 (JR1-157) and 17 (JR2-298) bind σ2R with Ki of 47 and 10 nM, respectively. Importantly, compound 14 has an oral bioavailability of 60% and shows significant in vivo efficacy without obvious toxicity in a syngeneic model of pancreatic cancer. The cytotoxicity of the quinolyl pyrazinamides significantly enhanced in the presence of copper and diminished in the presence of the copper-chelator tetrathiomolybdate. In conclusion, compound 14 is water-soluble, metabolically stable, orally active, and increases the expression of the autophagy marker LC3B and warrants further development for the treatment of pancreatic cancer.

Discovery of a Napabucasin PROTAC as an Effective Degrader of the E3 Ligase ZFP91.

Napabucasin, undergoing multiple clinical trials, was reported to inhibit the signal transducer and transcription factor 3 (STAT3). To better elucidate its mechanism of action, we designed a napabucasin-based proteolysis targeting chimera (PROTAC), XD2-149 that resulted in inhibition of STAT3 signaling in pancreatic cancer cell lines without inducing proteasome-dependent degradation of STAT3. Proteomics analysis of XD2-149 revealed the downregulation of the E3 ubiquitin-protein ligase ZFP91. XD2-149 degrades ZFP91 with DC50 values in the nanomolar range. The cytotoxicity of XD2-149 was significantly, but not fully, reduced with ZFP91 knockdown providing evidence for its multi-targeted mechanism of action. The NQO1 inhibitor, dicoumarol, rescued the cytotoxicity of XD2-149 but not ZFP91 degradation, suggesting that the NQO1-induced cell death is independent of ZFP91. ZFP91 plays a role in tumorigenesis and is involved in multiple oncogenic pathways including NF-κB and HIF-1α.

Synthesis and biological evaluation of novel 2-oxo-1,2-dihydroquinoline-4-carboxamide derivatives for the treatment of esophageal squamous cell carcinoma.

No new and effective treatments have been approved for the treatment of esophageal squamous cell carcinoma (ESCC) in the past decade. Cisplatin and 5-fluoruracil are the most commonly used drugs for this disease. In order to develop a new class of drugs effective in our ESCC phenotypic screens, we began a systematic approach to generate novel compounds based on the 2-oxo-1,2-dihydroquinoline-4-carboxamide fragment. Herein, we report on the synthesis and initial assessment of 55 new analogues in two ESCC cell lines. Some of the active analogues with IC50 values around 10 µM were tested in three additional cell lines. Our structure-activity relationships revealed remarkable alterations in the anti proliferative activities upon modest chemical modifications and autophagy modulation is a suggested mechanism of action.