Abstract LB006: PC14586: The first orally bioavailable small molecule reactivator of Y220C mutant p53 in clinical development

Mutations in the TP53 gene are the most frequent somatic alterations in human cancer; approximately 50% of all human cancers possess mutations in TP53. Missense mutations in TP53 which result in a non-functional protein are the most frequently identified, these occur across the gene, however most hotspot mutations are localized within the DNA binding domain of the protein. Y220C is one such hotspot mutation, prevalent in ~1.8% of TP53 mutant tumors. PC14586 was structurally designed to bind tightly to a crevice within the mutant protein (KD~2.5 nM). It is the first orally bioavailable small molecule and selective reactivator of Y220C mutant p53 protein in clinical development. In Y220C mutant human cell lines, PC14586 was shown to stabilize the Y220C mutant in the wild type conformation, resulting in reactivation of p53 transcriptional activity and subsequent expression of its target proteins (e.g. p21, MDM2, Bax, PUMA). The reactivation of p53 function is highly selective to Y220C mutant cells and results in arrest of the cell cycle in vitro (IC50 ~0.230-1.8 μM). PC14586 has favorable pharmaceutical properties in pre-clinical species. In nude mice bearing Y220C mutant NUGC3 gastric cancer xenograft tumors, oral administration of PC14586 results in a dose responsive anti-tumor effect, with a target efficacious dose of 100 mg/kg daily resulting in approximately 80% tumor regression after 3 weeks. This anti-tumor effect was driven by a dose responsive pharmacodynamic modulation of the mutant p53 target. In human xenografts, PC14586 was shown to convert Y220C mutant to the wildtype conformation, resulting in activation of p53 transcription. This was demonstrated by the measurement of a p53 mRNA transcriptional signature and at the protein level by increases in p21 and MDM2 in the tumor and Macrophage Inhibitory Cytokine-1 (MIC-1) in both the tumor and plasma. In a C57Bl/6J syngeneic xenograft model bearing the Y220C mutation, administration of PC14586 at 100 mg/kg orally resulted in complete tumor cure in 80% of mice. PC14586 is well tolerated by pre-clinical species and possesses a favorable development profile. The safety and efficacy of PC14586 is currently being evaluated in a seamless Phase I/II clinical study that is a biomarker driven, solid tumor agnostic trial with patients whose tumor bears the Y220C TP53 mutation (NCT study identifier NCT04585750).

Citation Format: Melissa Dumble, Lizhong Xu, Romyr Dominique, Binbin Liu, Hong Yang, Mary-Kate McBrayer, Dafydd Thomas, Bruce Fahr, Hongju Li, Kuo-Sen Huang, Kimberly Robell, Chris Mulligan, Brandon Russo, Anna Puzio-Kuter, Thomas Davis, Binh Vu. PC14586: The first orally bioavailable small molecule reactivator of Y220C mutant p53 in clinical development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB006.

Pyrido[2,3-d]pyrimidines: discovery and preliminary SAR of a novel series of DYRK1B and DYRK1A inhibitors

DYRK1B is a kinase over-expressed in certain cancer cells (including colon, ovarian, pancreatic, etc.). Recent publications have demonstrated inhibition of DYRK1B could be an attractive target for cancer therapy. From a data-mining effort, the team has discovered analogues of pyrido[2,3-d]pyrimidines as potent enantio-selective inhibitors of DYRK1B. Cells treated with a tool compound from this series showed the same cellular effects as down regulation of DYRK1B with siRNA. Such effects are consistent with the proposed mechanism of action. Progress of the SAR study is presented.

Effects of LTB4 receptor antagonism on pulmonary inflammation in rodents and non-human primates

Asthma, chronic obstructive pulmonary disease (COPD) and acute lung injury/acute respiratory distress syndrome (ALI/ARDS) are characterized by neutrophilic inflammation and elevated levels of leukotriene B4 (LTB4). However, the exact role of LTB4 pathways in mediating pulmonary neutrophilia and the potential therapeutic application of LTB4 receptor antagonists in these diseases remains controversial. Here we show that a novel dual BLT1 and BLT2 receptor antagonist, RO5101576, potently inhibited LTB4-evoked calcium mobilization in HL-60 cells and chemotaxis of human neutrophils. RO5101576 significantly attenuated LTB4-evoked pulmonary eosinophilia in guinea pigs. In non-human primates, RO5101576 inhibited allergen and ozone-evoked pulmonary neutrophilia, with comparable efficacy to budesonide (allergic responses). RO5101576 had no effects on LPS-evoked neutrophilia in guinea pigs and cigarette smoke-evoked neutrophilia in mice and rats. In toxicology studies RO5101576 was well-tolerated. Theses studies show differential effects of LTB4 receptor antagonism on neutrophil responses in vivo and suggest RO5101576 may represent a potential new treatment for pulmonary neutrophilia in asthma.

Discovery of AICAR Tfase inhibitors that disrupt requisite enzyme dimerization

The discovery of a new class of aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase) inhibitors through screening peptidomimetic libraries (>40,000 compounds) that act by inhibiting requisite enzyme dimerization is disclosed. In addition to defining key structural features of the lead compounds responsible for the activity, kinetic analysis of the remarkably small inhibitors established that they act as noncompetitive, dissociative inhibitors of AICAR Tfase with the prototypical lead (A1B3, Cappsin 1) exhibiting a K(i) of 3.1 +/- 0.3 microM. Thus, the studies define a unique approach to selectively targeting AICAR Tfase over all other folate-dependent enzymes, and it represents only one of a few enzymes for which inhibition achieved by disrupting requisite enzyme dimerization has emerged from screening unbiased combinatorial libraries.

A facile new procedure for the deprotection of allyl ethers under mild conditions

A novel isomerization of O-allyl glycosides into prop-1-enyl glycosides was observed instead of cross-metathesis during an olefin metathesis reaction using Grubbs' ruthenium benzylidene catalyst (Cy3P)2RuCl2=CHPh (1), N-allyltritylamine, and N,N-diisopropylethylamine as necessary auxiliary reagents. In the search for a better catalytic system, it has been found that dichlorotris(triphenylphosphine)ruthenium(II), [(C6H5)3P]3RuCl2, (2) was much more efficient for the isomerization of allylic ethers. The labile prop-1-enyl group was easily hydrolyzed using HgCl2-HgO and the hemiacetals (25-32) were isolated in excellent yields (ca. 90%).Key words: allyl ether, carbohydrate, Grubbs' catalyst, isomerization, metathesis, deprotection.

Extended Alkenyl Glycosides by Ruthenium-Catalyzed Cross-Metathesis Reaction and Application toward Novel C-Linked Pseudodisaccharides

Grubbs's ruthenium benzylidene catalyst (3) has been successfully applied toward the cross-metathesis reactions of allyl alpha-D-galactopyranoside derivative (4) with a number of olefins. Terminal alkenes possessing a wide range of protecting groups were used as cross-metathetic partners to allow syntheses of glycosides having extended spacers and functionality in the aglycon moieties. The reaction is quite general and the cross-metathesis products (14-21) were obtained in high yields. The strategy has also been applied toward the synthesis of some C-linked pseudodisaccharides from allyl alpha-C-galactoside derivatives (23, 26, and 28) in good yields. In almost all cases, trans-stereoselectivity was found to be good to excellent.

Multiple-pass cell for very-long-path infrared spectrometry

A multiple-pass cell for mid-IR spectrometry that has been designed to operate in an evacuable environmental chamber is described. Using this new modified White arrangement, we can significantly increase the path length while keeping the spectrometric beam stable. An approximate expression that ties the number of reflections to the optimal signal-to-noise ratio in multiple-reflection cells is derived.