Search

Supplementary Fig. S3 from Antitumor activity and pharmacokinetic properties of PF-00299804, a second-generation irreversible pan-erbB receptor tyrosine kinase inhibitor

Signaling through the erbB receptor family of tyrosine kinases contributes to the proliferation, differentiation, migration, and survival of a variety of cell types. Abnormalities in members of this receptor family have been shown to play a role in oncogenesis, thus making them attractive targets for anticancer treatments. PF-00299804 is a second-generation irreversible pan-erbB receptor tyrosine kinase inhibitor currently in phase I clinical trials. PF-00299804 is believed to irreversibly inhibit erbB tyrosine kinase activity through binding at the ATP site and covalent modification of nucleophilic cysteine residues in the catalytic domains of erbB family members. Oral administration of PF-00299804 causes significant antitumor activity, including marked tumor regressions in a variety of human tumor xenograft models that express and/or overexpress erbB family members or contain the double mutation (L858R/T790M) in erbB1 (EGFR) associated with resistance to gefitinib and erlotinib. Furthermore, PF-00299804 shows exceptional distribution to human tumor xenografts and excellent pharmacokinetic properties across species. [Mol Cancer Ther 2008;7(7):1880–9]

Lorlatinib is a potent small-molecule anaplastic lymphoma kinase inhibitor approved for the treatment of patients with nonsmall cell lung cancer. In a drug-drug interaction study in healthy human participants, liver enzyme elevations were observed when a single 100 mg dose of lorlatinib was administered after multiple doses of rifampin, a strong cytochrome P450 (CYP) 3A inducer and a pregnane X receptor (PXR) agonist. A series of in vitro and in vivo studies were conducted to evaluate potential mechanisms for the observed clinical toxicity. To investigate the involvement of CYP3A and/or PXR in the observed liver toxicity, studies were conducted in cynomolgus monkeys administered lorlatinib alone or with coadministration of multiple doses of known CYP3A inducers that are predominantly PXR agonists (rifampin, St. John’s wort) or predominantly constitutive androstane receptor agonists (carbamazepine, phenytoin) and a net CYP3A inhibitory PXR agonist (ritonavir). Results from the investigative studies identified cynomolgus monkeys as a pharmacologically relevant nonclinical model, which recapitulated the elevated liver function test results observed in humans. Furthermore, liver toxicity was only observed in this model when lorlatinib was coadministered with strong CYP3A inducers, and the effects were not restricted to, or exclusively dependent upon, a PXR activation mechanism. These results generated mechanistic insights on the liver enzyme elevations observed in the clinical drug-drug interaction study and provided guidance on appropriate product safety label for lorlatinib.

Peptide agonists of the glucagon-like peptide-1 receptor (GLP-1R) have revolutionized diabetes therapy, but their use has been limited by the requirement for injection. Here we describe the first effective, orally bioavailable small molecule GLP-1R agonists. A sensitized high-throughput screen identified a series of small molecule GLP-1R agonists that were optimized to promote endogenous GLP-1R signaling with nM potency. These small molecule agonists increased insulin levels in primates but not rodents, which is explained by a cryo-EM structure that revealed a binding pocket requiring primate-specific tryptophan 33. Importantly, oral administration of agonist PF-06882961 to healthy humans produced dose-dependent declines in serum glucose (NCT03309241). This opens the door to a new era of oral small molecule therapies that target the well-validated GLP-1R pathway for metabolic health.One Sentence SummaryPF-06882961 is an orally administered small molecule that activates the GLP-1 receptor to lower blood glucose in humans.

Glomerulopathy and body weight gain were noted after chronic oral administration of a novel nonsteroidal dissociated agonist of the glucocorticoid receptor compound, fosdagrocorat, to beagle dogs fed an ad libitum diet. To further investigate the role of diet and treatment with either fosdagrocorat or the glucocorticoid comparator, prednisone, on renal safety, a 13-week investigative study was conducted in beagle dogs. Renal histopathology, clinical chemistry, urinalysis, glomerular filtration rate (GFR), body weight, heart rate, blood pressure (BP), and hematology were investigated in restricted- and ad libitum-fed dogs administered prednisone (2.2 mg/kg/d), fosdagrocorat (5 mg/kg/d), or vehicle for 13 weeks. Glomerulopathy was primarily observed in fosdagrocorat- and prednisone-treated ad libitum but not in feed-restricted or ad libitum vehicle-treated dogs. Kidneys in dogs from the prednisone-treated ad libitum had the greatest incidence and severity of tubular degenerative changes. Increased urine volume and decreased urine-specific gravity were present in prednisone- and fosdagrocorat-treated dogs, regardless of diet. These changes were not associated with consistent changes in GFR. Fosdagrocorat or prednisone treatment ad libitum dogs had the greatest increase in body weight gain. Sporadic changes in systolic and diastolic BP were noted in fosdagrocorat- and prednisone-treated groups. Significant reductions in serum cortisol and absolute eosinophils were noted in both ad libitum- and restriction-fed prednisone- and fosdagrocorat-treated dogs. In conclusion, prednisone-treated dogs fed ad libitum had greater glucocorticoid-induced renal effects than those dosed with fosdagrocorat.

The discovery of two histamine H3 antagonist clinical candidates is disclosed. The pathway to identification of the two clinical candidates, 6 (PF-03654746) and 7 (PF-03654764) required five hypothesis driven design cycles. The key to success in identifying these clinical candidates was the development of a compound design strategy that leveraged medicinal chemistry knowledge and traditional assays in conjunction with computational and in vitro safety tools. Overall, clinical compounds 6 and 7 exceeded conservative safety margins and possessed optimal pharmacological and pharmacokinetic profiles, thus achieving our initial goal of identifying compounds with fully aligned oral drug attributes, “best-in-class” molecules.

The discovery of two histamine H(3) antagonist clinical candidates is disclosed. The pathway to identification of the two clinical candidates, 6 (PF-03654746) and 7 (PF-03654764) required five hypothesis driven design cycles. The key to success in identifying these clinical candidates was the development of a compound design strategy that leveraged medicinal chemistry knowledge and traditional assays in conjunction with computational and in vitro safety tools. Overall, clinical compounds 6 and 7 exceeded conservative safety margins and possessed optimal pharmacological and pharmacokinetic profiles, thus achieving our initial goal of identifying compounds with fully aligned oral drug attributes, "best-in-class" molecules.

Raf kinases (A-Raf, B-Raf, C-Raf) link Ras activation to MEK/ERK pathway activation, and are part of the key MAPK signaling pathway that controls cellular functions such as cell proliferation, migration, differentiation, and survival. Activating mutations in B-Raf occurs in a variety of cancers and inhibition of these signaling proteins in the pathway, therefore, represents a therapeutic targeting strategy for diverse cancers. We developed PF-04880594, an ATP-competitive and reversible inhibitor of B-Raf. To assess safety prior to initiation of clinical trials, repeat dose toxicity studies were performed in the rat and dog. Animals were treated orally at 0, 25, 75, 300→150 mg/kg/day in the rat or 0, 0.5, 6, 15→12 mg/kg/day in the dog for 30 days followed by a 30-day treatment-free period to assess recovery or delayed toxicity. Plasma concentrations of the B-Raf inhibitor were measured on Day 1 and at the end of the dosing phase of the study. Body weight and food consumption were measured at regular intervals and clinical signs were recorded daily. In the rat, dose-related clinical signs, occurring in the skin at ≥ 25 mg/kg included dry skin and/or edema in the paws, erythema and desquamation of tail skin > 75 mg/kg, and erythema of the ear at 300→150 mg/kg. In the dog, clinical signs observed at ≥ 6 mg/kg included desquamation and alopecia of the skin involving the ear, head, eyebrow, muzzle, thorax, lips, nose, scrotum or forepaw; and edema of the ear, muzzle, head, forepaw, hindpaw or scrotum. Erythema was observed at all dose levels on the muzzle, ear or head during life. In both species, these clinical signs correlated microscopically with epithelial hyperplasia in these affected tissues. Hyperplasia of the stratified epithelium of the tongue and esophagus occurred in both species, In the rat, epithelial hyperplasia was additionally observed in the urinary bladder and nonglandular stomach and dose-related proliferation of woven bone was observed primarily on endocortical surfaces in the proximal tibia and /or distal femur. Clinical pathology revealed an inflammatory response indicated by increased fibrinogen and neutrophil counts in dogs at ≥ 6 mg/kg (males > females) and in rats at ≥ 75 mg/kg. At the end of the recovery period, the inflammatory response and the woven bone changes were not evident, but epithelial hyperplasia was only partly resolved. A no-observed-effect-level was not identified in either study due to the epithelial hyperplasia. At low doses, margins of exposure were over 10-fold in the rat and 0.03-fold in the dog of projected clinically efficacious plasma concentration in humans. These studies indicate epithelial hyperplasia is paradoxically induced by this selective B-Raf inhibitor. The occurrence of this change in the rodent and canine suggests that this effect could develop in other mammalian species. Combination studies to test the effects of Raf and MEK inhibition on hyperplasia are currently being investigated. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1681.