Juthamas Sukbuntherng

Targeting BTK with Ibrutinib in Relapsed Chronic Lymphocytic Leukemia

BACKGROUND The treatment of relapsed chronic lymphocytic leukemia (CLL) has resulted in few durable remissions. Brutons tyrosine kinase (BTK), an essential component of B-cell-receptor signaling, mediates interactions with the tumor microenvironment and promotes the survival and proliferation of CLL cells. METHODS We conducted a phase 1b-2 multicenter study to assess the safety, efficacy, pharmacokinetics, and pharmacodynamics of ibrutinib (PCI-32765), a first-in-class, oral covalent inhibitor of BTK designed for treatment of B-cell cancers, in patients with relapsed or refractory CLL or small lymphocytic lymphoma. A total of 85 patients, the majority of whom were considered to have high-risk disease, received ibrutinib orally once daily; 51 received 420 mg, and 34 received 840 mg. RESULTS Toxic effects were predominantly grade 1 or 2 and included transient diarrhea, fatigue, and upper respiratory tract infection; thus, patients could receive extended treatment with minimal hematologic toxic effects. The overall response rate was the same in the group that received 420 mg and the group that received 840 mg (71%), and an additional 20% and 15% of patients in the respective groups had a partial response with lymphocytosis. The response was independent of clinical and genomic risk factors present before treatment, including advanced-stage disease, the number of previous therapies, and the 17p13.1 deletion. At 26 months, the estimated progression-free survival rate was 75% and the rate of overall survival was 83%. CONCLUSIONS Ibrutinib was associated with a high frequency of durable remissions in patients with relapsed or refractory CLL and small lymphocytic lymphoma, including patients with high-risk genetic lesions. (Funded by Pharmacyclics and others; ClinicalTrials.gov number, NCT01105247.).

Bruton Tyrosine Kinase Inhibitor Ibrutinib (PCI-32765) Has Significant Activity in Patients With Relapsed/Refractory B-Cell Malignancies

PURPOSE Survival and progression of mature B-cell malignancies depend on signals from the B-cell antigen receptor, and Bruton tyrosine kinase (BTK) is a critical signaling kinase in this pathway. We evaluated ibrutinib (PCI-32765), a small-molecule irreversible inhibitor of BTK, in patients with B-cell malignancies. PATIENTS AND METHODS Patients with relapsed or refractory B-cell lymphoma and chronic lymphocytic leukemia received escalating oral doses of ibrutinib. Two schedules were evaluated: one, 28 days on, 7 days off; and two, once-daily continuous dosing. Occupancy of BTK by ibrutinib in peripheral blood was monitored using a fluorescent affinity probe. Dose escalation proceeded until either the maximum-tolerated dose (MTD) was achieved or, in the absence of MTD, until three dose levels above full BTK occupancy by ibrutinib. Response was evaluated every two cycles. RESULTS Fifty-six patients with a variety of B-cell malignancies were treated over seven cohorts. Most adverse events were grade 1 and 2 in severity and self-limited. Dose-limiting events were not observed, even with prolonged dosing. Full occupancy of the BTK active site occurred at 2.5 mg/kg per day, and dose escalation continued to 12.5 mg/kg per day without reaching MTD. Pharmacokinetic data indicated rapid absorption and elimination, yet BTK occupancy was maintained for at least 24 hours, consistent with the irreversible mechanism. Objective response rate in 50 evaluable patients was 60%, including complete response of 16%. Median progression-free survival in all patients was 13.6 months. CONCLUSION Ibrutinib, a novel BTK-targeting inhibitor, is well tolerated, with substantial activity across B-cell histologies.

Effect of CYP3A perpetrators on ibrutinib exposure in healthy participants

Ibrutinib (PCI‐32765), a potent covalent inhibitor of Brutons tyrosine kinase, has shown efficacy against a variety of B‐cell malignancies. Given the prominent role of CYP3A in ibrutinib metabolism, effect of coadministration of CYP3A perpetrators with ibrutinib was evaluated in healthy adults. Ibrutinib (120 mg [Study 1, fasted], 560 mg [studies 2 (fasted), and 3 (nonfasted)]) was given alone and with ketoconazole [Study 1; 400 mg q.d.], rifampin [Study 2; 600 mg q.d.], and grapefruit juice [GFJ, Study 3]. Lower doses of ibrutinib were used together with CYP3A inhibitors [Study 1: 40 mg; Study 3: 140 mg], as safety precaution. Under fasted condition, ketoconazole increased ibrutinib dose‐normalized (DN) exposure [DN‐AUClast: 24‐fold; DN‐Cmax: 29‐fold], rifampin decreased ibrutinib exposure [Cmax: 13‐fold; AUClast: 10‐fold]. Under nonfasted condition, GFJ caused a moderate increase [DN‐Cmax: 3.5‐fold; DN‐AUC: 2.2‐fold], most likely through inhibition of intestinal CYP3A. Half‐life was not affected by CYP perpetrators indicating the interaction was mainly on first‐pass extraction. All treatments were well‐tolerated.

Impact of ibrutinib dose adherence on therapeutic efficacy in patients with previously treated CLL/SLL

Ibrutinib, an oral inhibitor of Brutons tyrosine kinase (BTK), at a once-daily dose of 420 mg achieved BTK active-site occupancy in patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) that was maintained at 24 hours. It is unknown if intermittent interruption of ibrutinib therapy contributes to altered clinical outcomes. We therefore evaluated the effect of ibrutinib dose adherence on patient outcomes in the phase 3 RESONATE trial. The overall mean dose intensity (DI) was 95% with median treatment duration of ∼9 months. Pharmacokinetic assessment of ibrutinib exposure at 420-mg dose suggested similar exposure regardless of patient weight or age. As assessed by independent review committee, patients with higher DI experienced longer median progression-free survival (PFS) compared with those with lower DI regardless of del17p and/or TP53 status. Of 79 patients requiring a drug hold, treatment was restarted at the original dose in 73 (92%) patients. Mean duration of a missed-dose event was 18.7 days (range, 8-56). Patients missing ≥8 consecutive days of ibrutinib had a shorter median PFS vs those missing <8 days (10.9 months vs not reached). These results support sustained adherence to once-daily ibrutinib dosing at 420 mg as clinically feasible to achieve optimal outcomes in patients with previously treated CLL. The trial was registered at www.clinicaltrials.gov as #NCT01578707.

Bioanalysis of ibrutinib and its active metabolite in human plasma: selectivity issue, impact assessment and resolution

Ronald de Vries graduated in Organic and Analytical Chemistry at the Free University of Amsterdam, The Netherlands. After working in a Contract Laboratory (CRO) for 7 years, he joined Janssen R&D in 1998. At Janssen R&D, Belgium, Ronald worked in the bioanalytical department that supports both clinical and nonclinical bioanalysis. In this department he had several roles, such as providing the bioanalytical support for various drug development programs and leading the method establishment group. He has done numerous global assay transfers to/from Janssen from/to other laboratories and plays an important role in the introduction and application of new technologies and applied innovation in the department. In 2014 he started in the drug metabolism and pharmacokinetics department of Janssen R&D, where his main tasks are in vivo and in vitro metabolite identification using high resolution MS and Radiodetection.

Abstract 4637: Evaluation of the pharmacokinetics and food effect of oral ibrutinib in healthy subjects and chronic lymphocytic leukemia patients

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy treated with chemoimmunotherapy. Such treatment results in high response rates but patients may eventually relapse and require alternate therapies. Ibrutinib (PCI-32765), a recently developed novel treatment, is unique in its mechanism as it inhibits Bruton9s tyrosine kinase, a key kinase in the B-cell receptor signaling pathway. It9s a Biopharmaceutics Classification Systems (BCS) class 2 compound and is metabolized rapidly by CYP3A. Three studies were conducted. The primary objectives were to assess the pharmacokinetics (PK) of ibrutinib under fed and fasted conditions and to assess the impact of food intake timing. Additionally, the safety and tolerability of ibrutinib were assessed. Study 1 was a randomized, open-label, single-center, single-dose, 4-way crossover study in 44 healthy subjects. Study 2 was a multicenter, randomized, repeated-dose crossover study in 16 patients with relapsed or refractory CLL. The ibrutinib dose was 420 mg in both. Study 3 was an open-label, single-center, sequential study to assess absolute bioavailability of ibrutinib 560 mg in 8 healthy subjects. Ibrutinib was well tolerated in these studies. There were no serious adverse events (AEs) or discontinuations due to an AE. There were no clinically significant changes in laboratory safety parameters, electrocardiograms, or vital signs. Administration of ibrutinib to healthy subjects under fasting conditions resulted in approximately 60% of exposure compared to drug intake either 30 min before or 2 h after a high-fat meal. When ibrutinib was taken 30 min after a meal, drug exposure was comparable to the dosing conditions of either 30 min before or 2 h after the meal. Study 2 revealed that under fed conditions, the maximum concentration was 2.24 times greater and the area under the curve was 1.65 times greater compared to the fasted conditions, but similar to uncontrolled food intake conditions. A similar food effect was observed in study 3, in which a standard meal was consumed starting 30 min after dosing. When corrected for repeated dosing in patients, the PK parameters in healthy subjects and patients were comparable. The observed food effect is most likely the result of a decreased (intestinal and hepatic) first-pass effect, rather than an effect on solubilization. Since ibrutinib is a highly permeable compound, residence time in the gut and liver cells could be reduced when mesenteric and portal vein blood flow is increased under fed conditions, making ibrutinib less available to CYP3A clearance. The effect on bioavailability may outweigh the higher clearance due to liver blood flow. In conclusion, food causes no more than a doubling in ibrutinib systemic exposure. Considering the favorable safety profile, ibrutinib can be administered with or without food. Citation Format: Jan de Jong, Juthamas Sukbuntherng, Donna Skee, Joe Murphy, Susan O9Brien, John C. Byrd, Danelle James, Peter Hellemans, Juhui James Jiao, Vijay Chauhan, Italo Poggesi, Erik Mannaert. Evaluation of the pharmacokinetics and food effect of oral ibrutinib in healthy subjects and chronic lymphocytic leukemia patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4637. doi:10.1158/1538-7445.AM2014-4637

Abstract 4634: Population pharmacokinetic model of ibrutinib, a Bruton's tyrosine kinase inhibitor, for the treatment of B-cell malignancies

Chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) are B-cell malignancies with initial high response rate to chemoimmunotherapy, but are largely considered incurable. Ibrutinib (PCI-32765), an oral Bruton9s tyrosine kinase inhibitor recently approved to treat MCL, is under development for other B-cell malignancies. We developed a population pharmacokinetic (PK) model for describing data collected to date in clinical trials with ibrutinib. Ibrutinib plasma data were available from 3 clinical trials: 1) a phase 1 dose-escalation study in recurrent B-cell malignancies (doses: 1.25-12.5 mg/kg and 560 mg fixed); 2) a phase 1b/2 dose-finding study in CLL (doses: 420 and 840 mg); 3) an open-label, phase 2, fixed-dose study in MCL (dose: 560 mg). Overall, ≈3477 observations were collected in 245 patients following single and repeated daily dosing on different treatment days. A 2-compartment model with sequential zero to first order absorption and first order elimination was implemented. Analyses were performed with a log-transform-both-sides approach. Additive and exponential models were used to describe residual and inter-individual variability, respectively. The first-order conditional estimation method was implemented using NONMEM v 7.1. A linear model constructed with data collected following single and repeated doses of ibrutinib at different dose levels demonstrated that the PK was dose and time independent. Ibrutinib was rapidly absorbed and was characterized by a high oral plasma clearance (≈1000 L/h with between-subject variability of 21.9%; this, for a dose of 560 mg, would lead to an average steady state concentration of ≈22 ng/mL, ie, ≈50 nM) and a high apparent volume of distribution at steady state (≈10,000 L). Though both values are confounded by absolute bioavailability, these values suggest that ibrutinib clearance and volume are high. The half-lives of distribution and terminal phases were estimated to be In conclusion, the proposed population PK model was able to accommodate the plasma concentration-time profiles of ibrutinib across various trials. Citation Format: Eleonora Marostica, Juthamas Sukbuntherng, David Loury, Jan De Jong, Xavier Woot de Trixhie, An Vermeulen, Giuseppe de Nicolao, Susan O9Brien, John C. Byrd, Ranjana Advani, Jesse McGreivy, Italo Poggesi. Population pharmacokinetic model of ibrutinib, a Bruton9s tyrosine kinase inhibitor, for the treatment of B-cell malignancies. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4634. doi:10.1158/1538-7445.AM2014-4634