Abstract P3-04-05: Identification of SAR439859, an orally bioavailable selective estrogen receptor degrader (SERD) that has strong antitumor activity in wild-type and mutant ER+ breast cancer models

Estrogen receptor positive (ER+) breast cancer accounts for 70% of all breast cancers and is primarily treated with endocrine therapy. Approximately 40% of patients on endocrine therapy will become resistant via a number of mechanisms. There is evidence that in many cases ER continues to play a central role, including mutations in ER leading to a constitutively active receptor. Estrogen receptor degraders like fulvestrant are effective in shutting down ER signaling; however, poor pharmaceutical properties limit fulvestrant clinical activity and prevent it from achieving maximum receptor blockade.

We describe the discovery of SAR439859, a novel, orally bioavailable SERD that is a potent antagonist and degrader of ER both in vitro and in vivo. SAR439859 has robust activity in multiple ER+ breast cancer cell lines including cells that are resistant to tamoxifen as well as cell lines harboring ER mutants. Across a large panel of ER+ cells, SAR439859 demonstrated broad and superior ER degradation activity than most SERDs undergoing clinical testing. This leads to a profound inhibition of ER signaling, better inhibition of cell growth and results in improved in vivo efficacy. SAR439859 demonstrated tumor regression in all ER+ BC models including MCF7-ESR1 mutant-Y537S model, as well as patient-derived xenograft model that is resistant to endocrine therapies. Furthermore, SAR439859 displays limited cross-resistance with other class of SERDs.

Taken together, these results suggest that SAR439859 would be of therapeutic benefit in metastatic BC setting for patients harboring wild type or mutant ER. SAR439859 is being advanced toward the clinic.

Citation Format: Shomali M, Cheng J, Koundinya M, Weinstein M, Malkova N, Sun F, Hebert A, Cindachao M, Hoffman D, McManus J, Levit M, Pollard J, Vincent S, Besret L, Adrian F, Winter C, El-Ahmad Y, Halley F, Hsu K, Lager J, Garcia-Echeverria C, Bouaboula M. Identification of SAR439859, an orally bioavailable selective estrogen receptor degrader (SERD) that has strong antitumor activity in wild-type and mutant ER+ breast cancer models [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-05.

RPR203494 a pyrimidine analogue of the p38 inhibitor RPR200765A with an improved in vitro potency

Following the discovery of RPR200765, a series of pyrimidine analogues have been prepared as backups. Amongst them, RPR203494 was identified with a better in vitro profile than RPR200765A.

The discovery of RPR 200765A, a p38 MAP kinase inhibitor displaying a good oral anti-arthritic efficacy

RPR132331, a 2-(2-dioxanyl)imidazole, was identified as an inhibitor of tumour necrosis factor (TNF)alpha release from lipopolysaccharide (LPS)-stimulated human monocytes. An intensive programme of work exploring the biology, toxicity and physical chemistry of a novel series of inhibitors, derived from RPR132331, has led to the identification of RPR200765A, a development candidate for the treatment of rheumatoid arthritis (RA). RPR200765A is a potent and selective inhibitor of p38 MAP kinase (IC50 = 50 nM). It inhibits LPS-stimulated TNFalpha release both in vitro, from human monocytes (EC50 = 110 nM), and in vivo in Balb/c mice (ED50 = 6 mg/kg). At oral doses between 10 and 30 mg/kg/day it reduces the incidence and progression in the rat streptococcal cell wall (SCW) arthritis model when administered in either prophylactic or therapeutic dosing regimens. The compound, which is a mesylate salt and exists as a stable monohydrate, shows good oral bioavailabiltiy (F = 50% in the rat) and excellent chemical stability. The data from the SCW disease model suggests that RPR200765A could exhibit a profile of disease modifying activity in rheumatoid arthritis (RA) patients which is not observed with current drug therapies.

Potential of p38 inhibitors in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic debilitating disease estimated to afflict 13% of the world population. Although palliative treatments (nonsteroidal antiinflammatory drugs or NSAIDs) are widely prescribed, there are currently only a few treatments that can modify the insidious progression of the disease (disease-modifying antirheumatic drugs or DMARDs), which frequently leads to physical incapacitation and, on occasion, death. Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) are implicated in the disease onset and in the progression of bone and joint destruction that characterizes chronic RA. p38 is an intracellular mitogen/stress-activated protein kinase (MAPK/SAPK) that regulates both the release and the actions of TNF-alpha and IL-1 beta. Inhibition of p38 kinase is thus an important potential target for novel DMARDs. Following the pioneering work conducted at SmithKline Beecham and elucidation of the roles of p38 with potent and selective inhibitors such as SB-203580, many pharmaceutical companies have embarked upon p38 synthetic programs, as indicated by the ever-increasing number of patents in this domain. At Aventis, a rapid parallel synthesis project led to the identification of RPR-200765A, a potent and selective p38 inhibitor of the lipopolysaccharide-induced release of TNF-alpha in vitro in mononuclear phagocytes and in vivo in the rat. It also reduces disease incidence and progression in the rat streptococcal cell wall arthritis model when administered orally in either a prophylactic or a therapeutic dosing regimen. Development of p38 inhibitors has been slow, probably because of toxicological problems, which might explain why only two oral p38 inhibitors, SB-242235 and VX-745, have advanced into clinical development. In the present article, the preclinical data exemplified in studies on RPR-200765A indicating why p38 inhibitors are attracting so much attention as potential novel anti-RA drugs are reviewed. Current information on the different structural classes of p38 inhibitors is presented and possible reasons for the delays in their development are critically discussed.

Selective ET(A) antagonists. 5. Discovery and structure-activity relationships of phenoxyphenylacetic acid derivatives

The fifth paper in this series describes the culmination of our investigations into the development of a potent and selective ET(A) receptor antagonist for the treatment of diseases mediated by ET-1. Receptor site mapping of several ET(A) antagonists prepared previously identified a common cationic binding site which prompted synthesis of phenoxyphenylacetic acid derivative 13a, which showed good in vitro activity (IC(50) 59 nM, rat aortic ET(A)). Optimization of 13a led to the identification of 27b, which exhibited an IC(50) of 4 nM. Although this did not translate into the expected in vivo potency, a compound of comparable in vitro activity, 27a (RPR118031A), showed a far better pharmacokinetic profile and in vivo potency (75 micromol/kg) and was duly proposed and accepted as a development candidate.

Recent advances in non-peptidic RANTES antagonists

RANTES is a member of a large family of cytokines, called chemokines, which are thought to play a regulatory role in leukocyte recruitment and inflammatory processes. The involvement of RANTES in diseases is now well documented and proved using antibody and peptide inhibitors. Non-peptidic RANTES antagonists, which have recently started to appear in the literature, will be reviewed.

Selective endothelin A receptor antagonists. 4. Discovery and structure-activity relationships of stilbene acid and alcohol derivatives

This publication describes the synthesis and optimization of a novel series of stilbene endothelin antagonists. Analysis of the SAR established for previous papers in this series prompted the design and synthesis of (Z)-4-phenyl-5-(3-benzyloxyphenyl)pent-4-enoic acid 3 which was found to be a moderately active inhibitor of the binding of [125I]ET-1 to ETA receptors with an IC50 of 6 microM. More interestingly, the intermediate compound (E)-2-phenyl-3-(3-benzyloxyphenyl)propenoic acid 5 was equiactive with 3. Optimization of 5 resulted in the preparation of (E)-2-phenyl-3-(2-cyano-5-(thien-3-ylmethoxy))phenylprope noic acid 18 (RPR111723) which had an IC50 in the binding assay of 80 nM on the ETA receptor and a pKB of 6.5 in the functional assay, measured on rat aortic strips. Reduction of the acid group of 5 gave the first nonacidic ETA antagonist in our series, (E)-2-phenyl-3-(3-benzyloxyphenoxy)prop2-enol 6 with an IC50 of 20 microM. Optimization of 6 resulted in the preparation of 2-(2-methylphenyl)-3-(2-cyano-5-(thien-3-ylmethyl)phenyl)pro p-2-enol 33 with an IC50 of 300 nM on the ETA receptor.

Identification of a non peptidic RANTES antagonist

A series of phenothiazines demonstrating inhibition of RANTES binding to THP-1 cell membranes has been identified. The lead compound RP23618 (IC50 = 3 microM) was found to inhibit specific binding of 125I-RANTES, but not 125I-MCP-1 to THP-1 cell membranes and furthermore to antagonize RANTES, but not MCP-1-induced chemotaxis of THP-1 cells.

New low-density lipoprotein receptor upregulators acting via a novel mechanism

The synthesis and biological activity of a new series of benzamides and related compounds that upregulate the expression of the low-density lipoprotein (LDL) receptor in human hepatocytes (HepG2 cells) by a novel mechanism are described. The lead compound, N-[5-[(3-cyclohexylpropionyl)amino]-2-methylphenyl]-4-hydroxybe nzamide (1, RPR102359), increased the expression of the LDL receptors in HepG2 cells by 80% when tested at a concentration of 3 microM. Mevinolin (lovastatin) was found to increase the LDL receptor expression by 70% at the same concentration. In contrast to mevinolin, 1 was found to have no effect on cholesterol biosynthesis in liver homogenates or in HepG2 cells at doses where substantial upregulation of the LDL receptor was observed and thus stimulated LDL receptor expression by a novel mechanism.