Analysis of a phase I pharmacokinetic (PK)/food effect study of AT-101 in patients with advanced solid tumors

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Background: AT-101 is an oral, pan-Bcl-2 inhibitor (Bcl-2, Bcl-XL, Bcl-W, Mcl-1). Overexpression of Bcl-2 family proteins is common in human cancers. AT-101 activity as a single agent as well as in combination with docetaxel has been reported. The ongoing Phase 1 study of AT-101 as a single agent was expanded to include a cohort of patients to determine the PK of AT-101 in fed and fasted states. Methods: Twelve patients (pts) were enrolled and randomized into cohorts of six pts each. Cohort A received AT-101 (80 mg) orally on day 1 on an empty stomach (fasted) and again on day 8 with a high fat high calorie breakfast (fed), per FDA guidelines. Cohort B received AT-101 on day 1 fed and on day 8 fasted. Preliminary plasma concentration time data for AT-101 from 10 patients administered 80 mg orally were evaluated using noncompartmental analysis. Log transformed peak concentration (Cmax) and exposure (AUC) were compared the between fed and fasted groups with the fasted group as the reference treatment. Results: Preliminary PK results from the first 10 pts are shown in the Table. For AUC and Cmax, the effect of food resulted in an approximately 42% and 5% increase, respectively. However the confidence intervals were not wholly outside the 80–125% intervals. Conclusions: These data indicate that food may increase AT-101 exposure in terms of AUC and Cmax. Updated results from all 12 pts will be presented at the meeting. Based on our preliminary results, it is recommended that AT-101 be taken at least an hour (or more) before or after food.

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[Table: see text]

A population pharmacokinetic-pharmacodynamic and logistic regression analysis of lotrafiban in patients

OBJECTIVE

Our objective was to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of lotrafiban, an oral glycoprotein IIb/IIIa inhibitor, in patients with a recent myocardial infarction, unstable angina, transient ischemic attack, or stroke.

METHODS

A 12-week, double-blind, multi-center, placebo-controlled, parallel-group, phase II study of lotrafiban (the Anti-platelet Useful Dose Study) was conducted in patients. Lotrafiban or placebo was administered as a twice daily oral dose at four dose levels (5-100 mg) for 12 weeks with daily doses of aspirin (300-325 mg). The pharmacokinetics of lotrafiban were characterized with the use of a population approach and were described by a two-compartment model with first order absorption and first order elimination. The pharmacodynamic data, ex vivo platelet aggregation, were described with the use of a direct effect inhibitory sigmoidal model with a baseline. The relationship between the severity of bleeding episodes and predicted steady-state lotrafiban exposure was characterized by logistic regression.

RESULTS

Pharmacokinetic analysis showed that increasing age and decreasing creatinine clearance resulted in increased exposure to lotrafiban. The concentration-effect relationship was steep, with near complete inhibition of platelet aggregation at lotrafiban concentrations in excess of 20 ng/mL. Logistic regression showed that at exposures that exceeded approximately 835 ng. h/mL, the severity of adverse bleeding events increased considerably; this suggested that dosing recommendations should be generated to minimize the likelihood of patients having an area under the plasma concentration-time curve from 0 to 24 hours in excess of this value.

CONCLUSIONS

Patients whose age exceeded 65 years or whose creatinine clearance was less than 60 mL/min should be given a lower dose of lotrafiban than younger patients with good renal function.

A phase I trial of humanized anti-interleukin 2 receptor antibody in renal transplantation

The efficacy of murine monoclonal anti-interleukin 2 alpha chain receptor (Tac) antibodies is limited by a short half-life and the development of antibodies to the heterologous protein. The safety, pharmacokinetics-dynamics, and immunosuppressive effect of a humanized anti-Tac antibody (HAT) was evaluated in 12 renal transplant recipients. Ten patients received living related transplants (three HLA-identical matches and seven one-haplotype or zero-haplotype matches) and two patients received cadaver organs. The patients were divided into four HAT treatment arms: 0.5 mg/kg/week (n=4), 1 mg/kg/week (n=2), 0.5 mg/kg every other week (n=3), and 1 mg/kg every other week (n=3). The first dose of HAT was given within 12 hr before transplantation, and four additional doses were given after transplantation. Patients were also placed on cyclosporine, steroids, and azathioprine. Only one patient, a recipient of a cadaver kidney in the lowest HAT treatment arm, had a reversible rejection episode. The 10 recipients of living related transplants were compared with 17 historical controls treated with an identical immunosuppressive regimen except for HAT. Whereas none of the HAT-treated living related donor recipients had a rejection episode, 6 of 17 (41%) of the historical controls had a rejection episode in the first year after transplantation. There were no first-dose reactions after HAT therapy or other subsequent side effects. None of the patients experienced opportunistic infections or malignancies. One patient developed low-titer anti-HAT antibodies, although the patient maintained high serum HAT concentrations throughout the study. Immune monitoring showed that there were no changes in the percentage or absolute counts of CD3 cells or T-cell subsets after HAT therapy. However, there was a significant decrease in the number of circulating lymphocytes that expressed free Tac. The overall harmonic mean half-life of HAT was 273 hr. The results of this study indicate that HAT given at 1 mg/kg every other week for a total of five doses may provide therapeutic HAT concentration levels and result in good saturation of Tac receptors for at least 12 weeks after transplantation. In summary, HAT is safe and is well tolerated by patients. Its long half-life and lack of immunization could make it a very useful immunosuppressive drug.

Use of an indirect pharmacodynamic stimulation model of MX protein induction to compare in vivo activity of interferon alfa-2a and a polyethylene glycol-modified derivative in healthy subjects

Interferon alfa-2a was chemically modified by the covalent attachment of a polyethylene glycol (PEG) moiety to enhance its circulating half-life and to reduce its immunogenicity. A comparative evaluation of the pharmacokinetics of the PEG-modified interferon alfa-2a showed a greater than twofold increase in the circulating half-life as a result of this chemical modification. An indirect physiologic response model was developed to characterize the time course of the MX protein response after subcutaneous administration of single ascending doses of either interferon alfa-2a or PEG-interferon alfa-2a in healthy volunteers. Analysis of the pharmacokinetic-pharmacodynamic relationship suggested that the PEG-modified interferon alfa-2a could not be administered less than twice weekly and therefore offered little therapeutic advantage over its unmodified counterpart, which is administered three times weekly. These results were consistent with findings in phase II trials. This study substantiates the usefulness of pharmacodynamic modeling as a tool for the development of dose recommendations and for the early selection of drug candidates in the drug development process.