Mohammad Javad Aman

Selpercatinib (LOXO292) and pralsetinib (BLU667) are RET protein tyrosine kinase inhibitors (TKIs) recently approved for treating RET-altered cancers. However, RET mutations that confer selpercatinib/pralsetinib resistance have been identified, necessitating development of next-generation RET TKIs. While acquired RET G810C/R/S/V mutations were reported in selpercatinib-treated patients, it was unclear whether all of these and other potential G810 mutants are resistant to selpercatinib and pralsetinib. Here, we profiled selpercatinib and pralsetinib on all six possible G810 mutants derived from single nucleotide substitution and developed novel alkynyl nicotinamide-based RET TKIs to inhibit selpercatinib/pralsetinib-resistant RET G810 mutants. Surprisingly, the G810V mutant found in a clinical study was not resistant to selpercatinib or pralsetinib. Besides G810C/R/S, G810D also conferred selpercatinib/pralsetinib resistance. Alkynyl nicotinamide compounds such as HSN608, HSL476, and HSL468 have better drug-like properties than alkynyl benzamides. Six of these compounds inhibited all six G810 solvent-front mutants and the V804M gatekeeper mutant with IC50 < 50 nmol/L in cell culture. Oral administration of HSN608 at a well-tolerated dose (30 mg/kg) gave plasma level > 30x the IC50s of inhibiting all G810 mutants in cell culture. In cell-derived xenograft tumors driven by KIF5B-RET (G810C) that contains the most frequently observed solvent-front mutant in selpercatinib-treated patients, HSN608, HSL476, and HSL468 significantly suppressed and caused regression of the selpercatinib-resistant tumors. This study clarifies the sensitivities of different RET solvent-front mutants to selpercatinib and pralsetinib and identifies novel alkylnyl nicotinamide-based RET TKIs for inhibiting selpercatinib/pralsetinib-resistant G810 mutants.

Anti-bacterial monoclonal antibody (mAb) therapies either rely on toxin neutralization or opsonophagocytic killing (OPK). Toxin neutralization protects the host from toxin-induced damage, while leaving the organism intact. OPK inducing antibodies clear the bacteria but leave the released toxins unencountered. Infection site targeted anti-toxin antibodies (ISTAbs) that we report here addresses this binary paradigm by combining both functionalities into a single molecule. ISTAbs consist of cell wall targeting (CWT) domains of bacteriophage endolysins fused to toxin neutralizing mAbs (IgG). CWT governs specific binding to the surface of bacteria while the IgG variable domain neutralizes the toxins as they are released. The complex is then cleared by phagocytic cells. As proof of concept, we generated several ISTAb prototypes targeting major toxins from two Gram-positive spore forming pathogens that have a high clinical significance; Clostridium difficile , causative agent of the most common hospital-acquired infection, and Bacillus anthracis , a Category A select agent pathogen. Both groups of ISTAbs exhibited potent toxin neutralization, binding to their respective bacterial cells, and induction of opsonophagocytosis. In mice infected with B. anthracis , ISTAbs exhibit significantly higher efficacy than parental IgG in both pre- and post-challenge models. Furthermore, ISTAbs fully protected against B. anthracis infection in a nonhuman primate (NHP) aerosol challenge model. These findings establish that as a platform technology, ISTAbs are broadly applicable for therapeutic intervention against several toxigenic bacterial pathogens.

Activating mutations of FLT3 contribute to deregulated hematopoietic stem and progenitor cell (HSC/Ps) growth and survival in patients with acute myeloid leukemia (AML), leading to poor overall survival. AML patients treated with investigational drugs targeting mutant FLT3 , including Quizartinib and Crenolanib, develop resistance to these drugs. Development of resistance is largely due to acquisition of cooccurring mutations and activation of additional survival pathways, as well as emergence of additional FLT3 mutations. Despite the high prevalence of FLT3 mutations and their clinical significance in AML, there are few targeted therapeutic options available. We have identified 2 novel nicotinamide-based FLT3 inhibitors (HSN608 and HSN748) that target FLT3 mutations at subnanomolar concentrations and are potently effective against drug-resistant secondary mutations of FLT3 . These compounds show antileukemic activity against FLT3 ^ITD in drug-resistant AML, relapsed/refractory AML, and in AML bearing a combination of epigenetic mutations of TET2 along with FLT3 ^ITD . We demonstrate that HSN748 outperformed the FDA-approved FLT3 inhibitor Gilteritinib in terms of inhibitory activity against FLT3 ^ITD in vivo.

Selpercatinib (LOXO292) and pralsetinib (BLU667) are RET protein tyrosine kinase inhibitors (TKIs) recently approved for treating RET-altered cancers. However, RET mutations that confer selpercatinib/pralsetinib resistance have been identified, necessitating development of next-generation RET TKIs. While acquired RET G810C/R/S/V mutations were reported in selpercatinib-treated patients, it was unclear whether all of these and other potential G810 mutants are resistant to selpercatinib and pralsetinib. Here, we profiled selpercatinib and pralsetinib on all six possible G810 mutants derived from single nucleotide substitution and developed novel alkynyl nicotinamide-based RET TKIs to inhibit selpercatinib/pralsetinib-resistant RET G810 mutants. Surprisingly, the G810V mutant found in a clinical study was not resistant to selpercatinib or pralsetinib. Besides G810C/R/S, G810D also conferred selpercatinib/pralsetinib resistance. Alkynyl nicotinamide compounds such as HSN608, HSL476, and HSL468 have better drug-like properties than alkynyl benzamides. Six of these compounds inhibited all six G810 solvent-front mutants and the V804M gatekeeper mutant with IC50 < 50 nmol/L in cell culture. Oral administration of HSN608 at a well-tolerated dose (30 mg/kg) gave plasma level > 30x the IC50s of inhibiting all G810 mutants in cell culture. In cell-derived xenograft tumors driven by KIF5B-RET (G810C) that contains the most frequently observed solvent-front mutant in selpercatinib-treated patients, HSN608, HSL476, and HSL468 significantly suppressed and caused regression of the selpercatinib-resistant tumors. This study clarifies the sensitivities of different RET solvent-front mutants to selpercatinib and pralsetinib and identifies novel alkylnyl nicotinamide-based RET TKIs for inhibiting selpercatinib/pralsetinib-resistant G810 mutants.

Selpercatinib (LOXO292) and pralsetinib (BLU667) are RET protein tyrosine kinase inhibitors (TKIs) recently approved for treating RET-altered cancers. However, RET mutations that confer selpercatinib/pralsetinib resistance have been identified, necessitating development of next-generation RET TKIs. While acquired RET G810C/R/S/V mutations were reported in selpercatinib-treated patients, it was unclear whether all of these and other potential G810 mutants are resistant to selpercatinib and pralsetinib. Here, we profiled selpercatinib and pralsetinib on all six possible G810 mutants derived from single nucleotide substitution, and developed novel alkynyl nicotinamide-based RET TKIs to inhibit selpercatinib/pralsetinib-resistant RET G810 mutants. Surprisingly, the G810V mutant found in a clinical study was not resistant to selpercatinib or pralsetinib. Besides G810C/R/S, G810D also conferred selpercatinib/pralsetinib resistance. Alkynyl nicotinamide compounds such as HSN608, HSL476, and HSL468 have better drug-like properties than alkynyl benzamides. Six of these compounds inhibited all six G810 solvent-front mutants and the V804M gatekeeper mutant with IC50 < 50 nmol/L in cell culture. Oral administration of HSN608 at a well-tolerated dose (30 mg/kg) gave plasma level > 30x the IC50s of inhibiting all G810 mutants in cell culture. In cell-derived xenograft tumors driven by KIF5B-RET (G810C) that contains the most frequently observed solvent-front mutant in selpercatinib-treated patients, HSN608, HSL476, and HSL468 significantly suppressed and caused regression of the selpercatinib-resistant tumors. This study clarifies the sensitivities of different RET solvent-front mutants to selpercatinib and pralsetinib, and identifies novel alkylnyl nicotinamide-based RET TKIs for inhibiting selpercatinib/pralsetinib-resistant G810 mutants.

Selpercatinib (LOXO292) and pralsetinib (BLU667) are RET protein tyrosine kinase inhibitors (TKIs) recently approved for treating RET-altered cancers. However, RET mutations that confer selpercatinib/pralsetinib resistance have been identified, necessitating development of next-generation RET TKIs. While acquired RET G810C/R/S/V mutations were reported in selpercatinib-treated patients, it was unclear whether all of these and other potential G810 mutants are resistant to selpercatinib and pralsetinib. Here, we profiled selpercatinib and pralsetinib on all six possible G810 mutants derived from single nucleotide substitution and developed novel alkynyl nicotinamide-based RET TKIs to inhibit selpercatinib/pralsetinib-resistant RET G810 mutants. Surprisingly, the G810V mutant found in a clinical study was not resistant to selpercatinib or pralsetinib. Besides G810C/R/S, G810D also conferred selpercatinib/pralsetinib resistance. Alkynyl nicotinamide compounds such as HSN608, HSL476, and HSL468 have better drug-like properties than alkynyl benzamides. Six of these compounds inhibited all six G810 solvent-front mutants and the V804M gatekeeper mutant with IC50 < 50 nmol/L in cell culture. Oral administration of HSN608 at a well-tolerated dose (30 mg/kg) gave plasma level > 30x the IC50s of inhibiting all G810 mutants in cell culture. In cell-derived xenograft tumors driven by KIF5B-RET (G810C) that contains the most frequently observed solvent-front mutant in selpercatinib-treated patients, HSN608, HSL476, and HSL468 significantly suppressed and caused regression of the selpercatinib-resistant tumors. This study clarifies the sensitivities of different RET solvent-front mutants to selpercatinib and pralsetinib and identifies novel alkylnyl nicotinamide-based RET TKIs for inhibiting selpercatinib/pralsetinib-resistant G810 mutants.