Inhibitors of the Hedgehog signaling pathway have generated a great deal of interest in the oncology area due to the mounting evidence of their potential to provide promising therapeutic options for patients. Herein, we describe the discovery strategy to overcome the issues inherent in lead structure 1 that resulted in the identification of 26), which has been advanced to human clinical studies.
PF-05231023, a long-acting fibroblast growth factor 21 (FGF21) analog, was generated by covalently conjugating two engineered [des-His1, Ala129Cys]FGF21 molecules to a nontargeting human IgG 1k scaffold. The pharmacokinetics (PK) of PF-05231023 after i.v. and s.c. administration was evaluated in rats and monkeys using two enzyme-linked immunosorbent assays with high specificity for biologically relevant intact N termini (NT) and C termini (CT) of FGF21. Intact CT of FGF21 displayed approximately 5-fold faster systemic plasma clearance (CL), an approximately 2-fold lower steady-state volume of distribution, and at least 5-fold lower bioavailability compared with NT. In vitro serum stability studies in monkeys and humans suggested that the principal CL mechanism for PF-05231023 was degradation by serum proteases. Direct scaling of in vitro serum degradation rates for intact CT of FGF21 underestimated in vivo CL 5-fold, 1.4-fold, and 2-fold in rats, monkeys, and humans, respectively. The reduced steady-state volume of distribution and the bioavailability for intact CT relative to NT in rats and monkeys were compatible with proteolytic degradation occurring outside the plasma compartment via an unidentified mechanism. Human CL and PK profiles for intact NT and CT of FGF21 were well predicted using monkey single-species allometric and Dedrick scaling. Physiologically based pharmacokinetic models incorporating serum stability data and an extravascular extraction term based on differential bioavailability of intact NT and CT of FGF21 in monkeys improved accuracy of human PK predictions relative to Dedrick scaling. Mechanistic physiologically based pharmacokinetic models of this nature may be highly valuable for predicting human PK of fusion proteins, synthetically conjugated proteins, and other complex biologics.
There are many sources of analytical variability in ligand binding assays (LBA). One strategy to reduce variability has been duplicate analyses. With recent advances in LBA technologies, it is conceivable that singlet analysis is possible. We retrospectively evaluated singlet analysis using Gyrolab data. Relative precision of duplicates compared to singlets was evaluated using 60 datasets from toxicokinetic (TK) or pharmacokinetic (PK) studies which contained over 23,000 replicate pairs composed of standards, quality control (QC), and animal samples measured with 23 different bioanalytical assays. The comparison was first done with standard curve and QCs followed by PK parameters (i.e., Cmax and AUC). Statistical analyses were performed on combined duplicate versus singlets using a concordance correlation coefficient (CCC), a measurement used to assess agreement. Variance component analyses were conducted on PK estimates to assess the relative analytical and biological variability. Overall, 97.5% of replicate pairs had a %CV of <11% and 50% of the results had a %CV of ≤1.38%. There was no observable bias in concentration comparing the first replicate with the second (CCC of 0.99746 and accuracy value of 1). The comparison of AUC and Cmax showed no observable difference between singlet and duplicate (CCC for AUC and Cmax >0.99999). Analysis of variance indicated an AUC inter-subject variability 35.3-fold greater than replicate variability and 8.5-fold greater for Cmax. Running replicates from the same sample will not significantly reduce variation or change PK parameters. These analyses indicated the majority of variance was inter-subject and supported the use of a singlet strategy.
A fixed-dose combination (FDC) of ertugliflozin, a selective sodium-glucose cotransporter 2 inhibitor, and immediaterelease metformin is approved for the treatment of type 2 diabetes mellitus in the United States and European Union. Four open-label, randomized, 2-period, single-dose, crossover studies were conducted under fasted conditions in healthy subjects to demonstrate bioequivalence of the ertugliflozin/metformin FDC tablets and coadministration of the individual components at respective strengths. In each study, 32 or 34 subjects received an ertugliflozin/metformin FDC tablet (2.5 mg/500 mg, 7.5 mg/850 mg, or 7.5 mg/1000 mg) and the respective doses of individual components (ertugliflozin with US-or EU-sourced metformin [Glucophage]). Plasma samples for ertugliflozin and metformin concentrations were collected for 72 hours in each period. For both ertugliflozin and metformin, the 90% confidence intervals for the adjusted geometric mean ratio (FDC : coadministration) for area under the plasma concentration-time profile from time zero extrapolated to infinity and maximum observed plasma concentration were within acceptance criteria for bioequivalence. The majority of adverse events were mild in intensity. The studies demonstrated that each strength of FDC tablet is bioequivalent to respective doses of coadministered individual components, supporting that safety and efficacy can be bridged to the individual components used in phase 3 studies evaluating ertugliflozin in combination with metformin.
This double‐blind, randomized, placebo‐controlled, dose‐ascending, first‐in‐human study (NCT02766621) assessed the safety, tolerability, and pharmacokinetics (PK) of PF‐06823859, an anti–interferon β monoclonal antibody. Healthy subjects were randomized to single ascending doses (SADs) of intravenous PF‐06823859 30, 100, 300, 900, or 2000 mg or placebo; to multiple ascending doses (MADs) of subcutaneous PF‐06823859 100 or 300 mg or placebo (once every 2 weeks for a total of 3 doses); or to MAD of intravenous PF‐06823859 600 mg or placebo (once every 3 weeks or once every 4 weeks for a total of 2 doses). The incidence, severity, and causal relationship of adverse events (AEs) were assessed, along with immunogenicity and PK. In total, 62 subjects were randomized to treatment (SAD, n = 35; MAD, n = 27). There were 76 treatment‐emergent all‐causality AEs in the SAD (PF‐06823859: n = 25; placebo: n = 4) and MAD (PF‐06823859: n = 40; placebo: n = 7) cohorts. In the SAD cohorts, all treatment‐emergent all‐causality AEs were mild in severity; 4 AEs of moderate severity were identified in the MAD cohorts. No dose‐limiting AEs, serious AEs, treatment‐related discontinuations, dose reductions, or deaths occurred. PF‐06823859 exposure increased dose‐proportionally, with half‐life values ranging between 23 and 35 days. The estimated subcutaneous bioavailability was 43% to 44%. Immunogenicity incidence rates were low (antidrug antibodies, 12.5%; neutralizing antibodies, 2.1%). No immunogenically related clinical responses of concern were observed. In conclusion, PF‐06823859 demonstrated an acceptable safety, tolerability, and PK profile that supports clinical development for treating disorders associated with increased interferon β levels, such as dermatomyositis or systemic lupus erythematosus.
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