Frank P. Hollinger

Discovery of Novel and Orally Bioavailable Inhibitors of PI3 Kinase Based on Indazole Substituted Morpholino-Triazines

A new class of potent PI3Kα inhibitors is identified based on aryl substituted morpholino-triazine scaffold. The identified compounds showed not only a high level of enzymatic and cellular potency in nanomolar range but also high oral bioavailability. The three lead molecules (based on their in vitro potency) when evaluated further for in vitro metabolic stability as well as pharmacokinetic profile led to the identification of 26, as a candidate for further development. The IC50 and EC50 value of 26 is 60 and 500 nM, respectively, for PI3Kα enzyme inhibitory activity and ovarian cancer (A2780) cell line. The identified lead also showed a high level of microsomal stability and minimal inhibition activity for CYP3A4, CYP2C19, and CYP2D6 at 10 μM concentrations. The lead compound 26, demonstrated excellent oral bioavailability with an AUC of 5.2 μM at a dose of 3 mpk in mice and found to be well tolerated in mice when dosed at 30 mpk BID for 5 days.

The N4 nitrogen of pirenzepine is responsible for selective binding of the M1 subtype human muscarinic receptor

Abstract An analog (SCH55112) of pirenzepine was prepared in which the N4 piperazyl nitrogen was replaced with carbon. This structrual change abolished the 55-fold m1/m2 selectivity of pirenzepine due to specific loss of m1 affinity. Mutagenesis mapping and modeling studies suggested this change was due to loss of a hydrogen bond to m1 Thr32 (m2Ala30).

Synthesis and evaluation of pyrrolotriazine based molecules as PI3 kinase inhibitors

Over activation of the PI3K/Akt/mTOR pathway is found in most cancer tumor types. Controlled regulation of this pathway using PI3K inhibitors can provide therapeutic significance in cancer treatment. Herein, we report the synthesis and evaluation of pyrrolotriazine based novel small molecules as pan-PI3K inhibitors. The SAR studies based on in vitro potency along with microsomal metabolic stability screening, identified 18 as a preclinical lead found to be suitable for in vivo evaluation. The identified lead was also found to be a selective inhibitor of PI3K isoforms and mTOR when screened across a panel of 23 homologous kinases.

Abstract 4515: SPR965: an oral PI3K/ mTOR C1/C2 inhibitor for the treatment of solid tumors

Background The discovery and development of inhibitors for the PI3K/AKT/mTOR signaling pathway is an attractive area of research due to its association with several oncogenic malignancies. This signaling pathway controls cellular growth as well as survival via regulation of widely divergent physiological processes, i.e. cell cycle progression, differentiation, transcription, translation and apoptosis. Constitutive activation of the PI3 kinase alpha and/or the downstream protein mTOR has been implicated in the progression of a large variety of solid tumors. Literature reports suggest the importance of developing combined and specific inhibitor of both PI3K and mTOR kinases. Described herein is the discovery of a novel small molecule, SPR965, a potent, and orally bioavailable inhibitor for class 1 PI3 Kinase and mTOR kinases with the potential for the clinical treatment of various solid tumors, specifically prostate, ovarian and colon cancers. The complete preclinical profile of SPR965 is presented in detail. Methods Drug candidates were evaluated in an in vitro enzyme assays to determine their inhibitory activity PI3 and mTOR C1/ C2 kinases. Promising candidates were then evaluated in proliferation assays using various human cancer cell lines (PC3 - prostate, SKOV3 - ovarian, HCT-116 - colon and A2780 - ovarian). The most promising leads were then evaluated against a panel of 456 kinases to determine the level of selectivity for our primary targets - PI3K and mTOR C1/C2. Compounds meeting the desired threshold of potency and selectivity were evaluated for their in vivo pharmacokinetic profile (iv/ po) in rodents followed by studies in mouse xenograft models (SKOV3 and HCT-116). Results SPR965 is a potent inhibitor of PI3K alpha and mTOR with an IC50 of 24 and 25 nM respectively. SPR965 is also a highly selective inhibitor of PI3 and mTOR C1/C2 kinases when evaluated in a screen against 456 kinases. Further studies demonstrated that SPR965 is a potent inhibitor of proliferation in a multiple cell lines and in several xenograft models. The proliferation inhibition activity (EC50) in A2780 is 17 nM, PC3 is 30 nM, SKOV3 is 74 nM, and HCT-116 is 163 nM. SPR965 is one of the most efficacious PI3/mTOR kinase inhibitor yet reported, with ED50 = 0.5 mg/Kg as determined in a SKOV3 xenograft mouse model and ED50 = 0.6 mg/ Kg in HCT-116 xenograft mouse model. This dose level is markedly lower than those reported for other reported inhibitors of this pathway. Pharmacokinetic studies in Sprague Dawley rats and in NUDE mice indicated that the oral bioavailability of SPR965was ∼100% and 75% respectively. Conclusion SPR965 is one of the most efficacious inhibitor of the PI3 and mTOR kinases when compared to the reported ED50s of other reported compounds. It also is one of the most selective and highly bioavailable inhibitor of the PI3 and mTOR kinases. Further studies are underway to support first-in-human trials with SPR965 where we hope to demonstrate its unique therapeutic benefits. Citation Format: Reena Arora, Bakul K. Dutta, Ravinder Goel, Frank P. Hollinger, Bilash Kulia, Dinesh Mahajan, Amal R. Mahapatra, Milind Sagar, Somdutta Sen, Amit Sharma, Sundeep Dugar. SPR965: an oral PI3K/ mTOR C1/C2 inhibitor for the treatment of solid tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4515. doi:10.1158/1538-7445.AM2014-4515