Location matters: site of conjugation modulates stability and pharmacokinetics of antibody drug conjugates.

Antibody drug conjugates (ADCs) are a therapeutic class offering promise for cancer therapy. The attachment of cytotoxic drugs to antibodies can result in an effective therapy with better safety potential than nontargeted cytotoxics. To understand the role of conjugation site, we developed an enzymatic method for site-specific antibody drug conjugation using microbial transglutaminase. This allowed us to attach diverse compounds at multiple positions and investigate how the site influences stability, toxicity, and efficacy. We show that the conjugation site has significant impact on ADC stability and pharmacokinetics in a species-dependent manner. These differences can be directly attributed to the position of the linkage rather than the chemical instability, as was observed with a maleimide linkage. With this method, it is possible to produce homogeneous ADCs and tune their properties to maximize the therapeutic window.

Discovery of a series of 2-(1H-pyrazol-1-yl)pyridines as ALK5 inhibitors with potential utility in the prevention of dermal scarring.

A series of 2-(1H-pyrazol-1-yl)pyridines are described as inhibitors of ALK5 (TGFß receptor I kinase). Modeling compounds in the ALK5 kinase domain enabled some optimization of potency via substitutions on the pyrazole core. One of these compounds PF-03671148 gave a dose dependent reduction in TGFß induced fibrotic gene expression in human fibroblasts. A similar reduction in fibrotic gene expression was observed when PF-03671148 was applied topically in a rat wound repair model. Thus these compounds have potential utility for the prevention of dermal scarring.

Discovery of a series of imidazo[4,5-b]pyridines with dual activity at angiotensin II type 1 receptor and peroxisome proliferator-activated receptor-γ.

Mining of an in-house collection of angiotensin II type 1 receptor antagonists to identify compounds with activity at the peroxisome proliferator-activated receptor-γ (PPARγ) revealed a new series of imidazo[4,5-b]pyridines 2 possessing activity at these two receptors. Early availability of the crystal structure of the lead compound 2a bound to the ligand binding domain of human PPARγ confirmed the mode of interaction of this scaffold to the nuclear receptor and assisted in the optimization of PPARγ activity. Among the new compounds, (S)-3-(5-(2-(1H-tetrazol-5-yl)phenyl)-2,3-dihydro-1H-inden-1-yl)-2-ethyl-5-isobutyl-7-methyl-3H-imidazo[4,5-b]pyridine (2l) was identified as a potent angiotensin II type I receptor blocker (IC(50) = 1.6 nM) with partial PPARγ agonism (EC(50) = 212 nM, 31% max) and oral bioavailability in rat. The dual pharmacology of 2l was demonstrated in animal models of hypertension (SHR) and insulin resistance (ZDF rat). In the SHR, 2l was highly efficacious in lowering blood pressure, while robust lowering of glucose and triglycerides was observed in the male ZDF rat.

Discovery of highly potent and selective benzyloxybenzyl-based peroxisome proliferator-activator receptor (PPAR) delta agonists.

A series of 1,4-benzyloxybenzylsulfanylaryl carboxylic acids were prepared and their activities for PPAR receptor subtypes (alpha, delta, and gamma) with potential indications for the treatment of dyslipidemia were investigated. Analog 13a displayed the greatest binding affinity (IC(50)=10nM) and selectivity (120-fold) for PPARdelta over PPARalpha. Many of the analogs investigated were found to be highly selective for PPARdelta and were dependent on the point of attachment of the substituent. In the 1,4-series, analog 28e was found to be the most potent (IC(50)=1.7 nM) and selective (>1000-fold) compound for PPARdelta. None of the compounds tested showed appreciable binding affinity for PPARgamma.

Synthesis and SAR of selective benzothiophene, benzofuran, and indole-based peroxisome proliferator-activated receptor delta agonists.

Recent literature has suggested the benefit of selective PPARdelta agonists for the treatment of atherosclerosis and other disease states associated with the metabolic syndrome. Herein we report the synthesis and structure-activity relationships of a series of novel and selective PPARdelta agonists. Our search began with identification of a novel benzothiophene template which was modified by the addition of various thiazolyl, isoxazolyl, and benzyloxy-benzyl moieties. Further elucidation of the SAR led to the identification of benzofuran and indole based templates. During the course of our research, we discovered three new chemical templates with varying degrees of affinity and potency for PPARdelta versus the PPARalpha and PPARgamma subtypes.