Population modeling of bosutinib exposure-response in patients with newly diagnosed chronic phase chronic myeloid leukemia.

BACKGROUND: The BELA and BFORE trials compared bosutinib starting doses of 500 mg once daily (QD) and 400 mg QD, respectively, with imatinib in adults with newly diagnosed chronic phase chronic myeloid leukemia (CP-CML). The B1871048 trial evaluated bosutinib 400 mg QD in Japanese patients with newly diagnosed CP-CML. AIM: This analysis assessed the impact of a lower bosutinib starting dose on key efficacy and safety outcomes. MATERIALS & METHODS: A pharmacokinetic model was used to estimate metrics of bosutinib exposure, and logistic regression was used to investigate relationships with efficacy (cumulative major molecular response [MMR] and cumulative complete cytogenetic response [CCyR]) and safety outcomes (eight prespecified adverse events). RESULTS: Totals of 573 and 574 patients were included in the efficacy and safety endpoint analyses, respectively. Cumulative MMR and CCyR were similar across studies. Log(Ctrough ) and log(Cavg ) were significant predictors of MMR and CCyR, and the probability of achieving MMR or CCyR increased 1.3-fold or 2.7-fold for every 1 unit increase in log(Ctrough ) or log(Cavg ), respectively. An exposure-response relationship was identified between time-to-event and risk of diarrhea, nausea, and vomiting. Significant relationships were also observed between time-to-event and log(Cavg ), Ctrough , and Cavg with diarrhea, nausea, and vomiting, respectively. DISCUSSION: A bosutinib exposure-response relationship with safety and efficacy was observed. CONCLUSION: Compared with 500 mg QD, a bosutinib starting dose of 400 mg QD improved tolerability in some patients with newly diagnosed CP-CML without compromising efficacy. CLINICALTRIALS: gov identifiers: NCT00574873; NCT02130557; NCT03128411.

Discovery of the Bruton's Tyrosine Kinase Inhibitor Clinical Candidate TAK-020 (S)-5-(1-((1-Acryloylpyrrolidin-3-yl)oxy)isoquinolin-3-yl)-2,4-dihydro-3H-1,2,4-triazol-3-one, by Fragment-Based Drug Design.

This publication details the successful use of FBDD (fragment-based drug discovery) principles in the invention of a novel covalent Bruton's tyrosine kinase inhibitor, which ultimately became the Takeda Pharmaceuticals clinical candidate TAK-020. Described herein are the discovery of the fragment 5-phenyl-2,4-dihydro-3H-1,2,4-triazol-3-one, the subsequent optimization of this hit molecule to the candidate, and synthesis and performance in pharmacodynamic and efficacy models along with direct biophysical comparison of TAK-020 with other clinical-level assets and the marketed drug Ibrutinib.

Population Pharmacokinetics of Gemtuzumab Ozogamicin in Pediatric Patients with Relapsed or Refractory Acute Myeloid Leukemia.

BACKGROUND AND OBJECTIVE: To date, the population pharmacokinetics (popPK) of gemtuzumab ozogamicin (GO), a CD33-directed antibody-drug conjugate consisting of hP67.6 antibody linked to N-acetyl gamma calicheamicin used in the treatment of acute myeloid leukemia (AML), has not been characterized in pediatric patients. This report describes the popPK of GO following intravenous administration in 29 pediatric patients aged ≤ 17 years with relapsed or refractory AML who were enrolled in the 0903A1-102-US phase I/II study. METHODS: The pharmacokinetics (PK) of GO, as represented by total hP67.6 antibody, were described by a two-compartment model with two clearance components: a linear clearance (CL1) and time-dependent clearance that includes a decay coefficient. The PK of unconjugated calicheamicin (UC; payload) were described by a two-compartment model with CL1 and an input rate of formation based on antibody rate of elimination. Allometric scaling was included in both models, with baseline body weight as a fixed effect on CL1 and central volume. RESULTS AND CONCLUSIONS: PK parameters for hP67.6 and UC were not significantly affected by any of the available demographic factors and safety laboratory values tested as covariates (except baseline body weight). Simulations to compare GO dosing regimens (6, 7.5, and 9 mg/m2 on days 1 and 15 versus, 3 mg/m2 fractionated dosing on days 1, 4, and 7) were performed, showing that total antibody and UC trough concentrations were maintained at higher concentrations during treatment following the more frequent dosing than following the original regimen. STUDY IDENTIFIER: 0903A1-102-US.

Population Pharmacokinetic Modeling of Gemtuzumab Ozogamicin in Adult Patients with Acute Myeloid Leukemia.

BACKGROUND AND OBJECTIVE: Gemtuzumab ozogamicin is an antibody-drug conjugate composed of the anti-CD33 monoclonal antibody hP67.6 covalently linked to N-acetyl-gamma-calicheamicin dimethylhydrazide, a potent cytotoxic antibiotic. The aim of this study was to characterize the population pharmacokinetics of gemtuzumab ozogamicin, represented by total hP67.6 antibody and unconjugated calicheamicin, in adult patients with acute myeloid leukemia to support drug dosing strategies and explore intrinsic and extrinsic factors that may influence exposure. Pharmacokinetic data from seven previous phase I and II studies in adult patients with relapsed, refractory, or de novo acute myeloid leukemia were integrated and analyzed using nonlinear mixed-effects modeling. METHODS: The pharmacokinetics of total hP67.6 antibody was described in 407 patients (5643 concentrations) who received gemtuzumab ozogamicin doses ranging from 0.25 to 9 mg/m2 using a two-compartment model with linear and time-dependent clearance components. The pharmacokinetics of unconjugated calicheamicin was characterized in 338 patients (4281 concentrations) using a two-compartment model with an input rate of formation dependent on the amount of hP67.6 eliminated. No statistically significant baseline covariates (sex, albumin, bone marrow, and peripheral blast percentage) demonstrated a clinically meaningful impact. RESULTS AND CONCLUSION: Total hP67.6 antibody disposition did not appear altered in patients with mild or moderate renal disease or hepatic impairment. Gemtuzumab ozogamicin was approved for the treatment of acute myeloid leukemia by the US Food and Drug Administration in September 2017. The model-based simulations described here provided a pharmacokinetic rationale for the approved dosing regimen of 3 mg/m2 on days 1, 4, and 7, and served as the basis for all exposure-response modeling included in the recent Biologics License Application submission. Clinical trials identifiers: 0903A1-101-US; 0903A1-103-JA; 0903B1-201-US/CA (NCT00003131); 0903B1-202-EU; 0903B1-203-US/EU (NCT00003673); 0903B1-205-US/EU/AU (NCT00037596); and 0903B1-206-US/EU/AU (NCT00037583).

A phase I pharmacokinetics study comparing PF-06439535 (a potential biosimilar) with bevacizumab in healthy male volunteers.

PURPOSE: This study compared the pharmacokinetics of PF-06439535, a potential bevacizumab biosimilar, to bevacizumab sourced from the European Union (bevacizumab-EU) and USA (bevacizumab-US), and of bevacizumab-EU to bevacizumab-US. METHODS: In this double-blind study, 102 healthy males, aged 21-55 years, were randomized 1:1:1 to receive a single 5 mg/kg intravenous dose of PF-06439535, bevacizumab-EU, or bevacizumab-US. Pharmacokinetic assessments were conducted for 71 days, with additional safety and immunogenicity assessments until day 100. Pharmacokinetic similarity was achieved if 90 % confidence intervals (CIs) for the test-to-reference ratios of the maximum serum concentration (C max), area under the serum concentration-time curve from zero to infinity (AUC0-∞), and from zero to time of last quantifiable concentration (AUC0-t ) were within the 80.00-125.00 % bioequivalence acceptance window. RESULTS: The three study drugs exhibited similar pharmacokinetic properties. For the comparisons of PF-06439535 to bevacizumab-EU or bevacizumab-US, and of bevacizumab-EU to bevacizumab-US, the 90 % CIs for the ratios of C max, AUC0-t , and AUC0-∞ were all within 80.00-125.00 %. Two, one, and two subjects treated with PF-06439535, bevacizumab-EU, and bevacizumab-US, respectively, tested positive for antidrug antibodies, none of whom tested positive for neutralizing antibodies. Treatment-related adverse events were reported in 15.2, 25.7, and 18.2 % of subjects in the PF-06439535, bevacizumab-EU, and bevacizumab-US treatment arms, respectively. CONCLUSIONS: This study demonstrated the pharmacokinetic similarity of PF-06439535 to both bevacizumab-EU and bevacizumab-US, and of bevacizumab-EU to bevacizumab-US. The safety profile (including immunogenicity) was similar in the three treatment groups, with no significant safety findings reported.

Fragment-Based Discovery of a Small Molecule Inhibitor of Bruton's Tyrosine Kinase.

The discovery and optimization of a series of 4-aminocinnoline-3-carboxamide inhibitors of Bruton's tyrosine kinase are reported. A fragment-based screening approach incorporating X-ray co-crystallography was used to identify a cinnoline fragment and characterize its binding mode in the ATP binding site of Btk. Optimization of the fragment hit resulted in the identification of a lead compound which reduced paw swelling in a dose- and exposure-dependent fashion in a rat model of collagen-induced arthritis.

P-glycoprotein increases portal bioavailability of loperamide in mouse by reducing first-pass intestinal metabolism.

P-glycoprotein (P-gp) and CYP3A (cytochrome P450 3A, generally; Cyp3a, rodent enzyme) in the intestine can attenuate absorption of orally administered drugs. While some suggest that P-gp enhances intestinal metabolism by CYP3A/Cyp3a during absorption of a dual substrate, others suggest that P-gp reduces the metabolism in the intestine when substrates are at subsaturating concentrations. Hence, to elucidate the cellular mechanisms that can address these divergent reports, we studied intestinal absorption of the dual substrate loperamide in portal vein-cannulated P-gp-competent and P-gp-deficient mice. These studies showed that at low doses of loperamide, which produced intestinal concentrations near the apparent K(m) for oxidative metabolism, the bioavailability across the intestine (F(G)) was 6-fold greater in the P-gp-competent mice than in P-gp-deficient mice. The higher F(G) of loperamide in the presence of P-gp was attributed to lower loperamide intestinal metabolism. However, at high doses of loperamide, the sparing of first-pass metabolism by P-gp was balanced against the attenuation of absorption by apical efflux, resulting in no net effect on F(G). In vitro studies with intestinal tissue from P-gp-competent and -deficient mice confirmed that P-gp reduced the metabolic rate of loperamide during absorptive flux at concentrations near K(m) but had little effect on metabolism at higher (saturating) concentrations. Further, studies in which Cyp3a was chemically inactivated by aminobenzotriazole in P-gp-competent and -deficient mice, showed that P-gp and Cyp3a individually attenuated F(G) by 8-fold and 70-fold, respectively. These results confirmed that P-gp effectively protects loperamide at low doses from intestinal first-pass metabolism during intestinal absorption.

Vectorial transport of fexofenadine across Caco-2 cells: involvement of apical uptake and basolateral efflux transporters.

Fexofenadine is a nonsedative antihistamine that exhibits good oral bioavailability despite its zwitterionic chemical structure and efflux by P-gp. Evidence exists that multiple uptake and efflux transporters play a role in hepatic disposition of fexofenadine. However, the roles of specific transporters and their interrelationship in intestinal absorption of this drug are unclear. This study was designed to elucidate vectorial absorptive transport of fexofenadine across Caco-2 cells involving specific apical uptake and efflux transporters as well as basolateral efflux transporters. Studies with cellular models expressing single transporters showed that OATP2B1 expression stimulated uptake of fexofenadine at pH 6.0. Apical uptake of fexofenadine into Caco-2 cells was decreased by 45% by pretreatment with estrone 3-sulfate, an OATP inhibitor, at pH 6.0 but not at pH 7.4, indicating that OATP2B1 mediates apical uptake of fexofenadine into these cells. Examination of fexofenadine efflux from preloaded Caco-2 cells in the presence or absence of (i) the MRP inhibitor MK-571 and (ii) the P-gp inhibitor GW918 showed that apical efflux is predominantly mediated by P-gp, with a small contribution by MRP2, whereas basolateral efflux is predominantly mediated by MRP3. These results also showed that while OSTαß is functionally active in the basolateral membrane of Caco-2 cells, it does not play a role in the export of fexofenadine. MK-571 decreased the absorptive transport of fexofenadine by 17%. However, the decrease in absorptive transport by MK-571 was 42% when P-gp was inhibited by GW918. The results provide a novel insight into a vectorial transport system mainly consisting of apical OATP2B1 and basolateral MRP3 that may play an important role in delivering hydrophilic anionic and zwitterionic drugs such as pravastatin and fexofenadine into systemic circulation upon oral administration.

Deconvoluting the effects of P-glycoprotein on intestinal CYP3A: a major challenge.

Metabolism by cytochrome P4503A (CYP3A) and P-glycoprotein (P-gp)-mediated efflux are two important biochemical barriers to drug absorption from the intestine. CYP3A, the most important family of drug-metabolizing enzymes, shares many substrates with the efflux transporter P-gp. Although the individual impact of these two systems on drug disposition is routinely assessed, the effect of both systems acting together during intestinal absorption is difficult to ascertain. Pharmacokinetic theory predicts that the effect of efflux on overall metabolism depends on substrate concentrations relative to the respective kinetic parameters of these processes (i.e. affinities for transport and metabolism, as well as the capacities of these processes). Researchers have published conflicting findings on how efflux affects metabolism. Furthermore, the in vitro parameters that have been used to explain or predict this interation are more relevant for describing overall changes in extraction efficiency of the system (intestinal epithelium), rather than deconvoluting the effect of P-gp on CYP3A-mediated metabolism. Developing a more refined way to understand this interplay and its potential relevance to drug absorption is an important goal, as a large proportion of marketed drugs and many modern drug discovery candidates are known to be affected by one or both of these proteins.