Randomized phase 2 therapeutic equivalence study of abiraterone acetate fine particle formulation vs. originator abiraterone acetate in patients with metastatic castration-resistant prostate cancer: The STAAR study.

BACKGROUND: This multicenter, randomized, open-label, active-controlled study evaluated therapeutic equivalence, steady-state pharmacokinetics, and safety of a novel abiraterone acetate fine particle formulation (AAFP) 500mg plus methylprednisolone vs. the originator AA (OAA) 1000mg plus prednisone in men with metastatic castrate-resistant prostate cancer (mCRPC). The primary endpoint was a comparison of average of serum testosterone levels on treatment days 9 and 10 between groups. METHODS: Men with progressive mCRPC, receiving gonadotropin-releasing hormone agonist or antagonist therapy, and with a serum testosterone level of <50ng/dl were randomized 1:1 to either AAFP 500mg daily plus 4mg methylprednisolone orally twice daily (BID), or OAA 1000mg daily plus 5mg prednisone BID for 84 days. Serum testosterone, serum prostate-specific antigen (PSA), steady-state (trough) abiraterone pharmacokinetics, and safety were evaluated. RESULTS: Fifty-three patients were enrolled (n = 24, AAFP; n = 29, OAA). Mean age was 75.1 years and 54.7% had Gleason>7. Over 90% of patients in each group achieved absolute testosterone levels of ≤1ng/dl during the study. The averaged absolute testosterone levels ≤0.1ng/dl were achieved in 25% of AAFP-treated patients and 17% of OAA-treated patients. A PSA-50 response was observed in>65% of patients in both groups on days 28, 56, and 84 (P = NS, all timepoints). Days 9 and 10 averaged rounded-up least squares (LS) mean (SE) serum testosterone levels were comparable (1.05ng/dl [0.04], AAFP; 1.02ng/dl [0.03], OAA; P = 0.4703 for LS mean difference). The geometric mean ratio between groups was 1.021 (90% CI: 0.965-1.081); the 90% CI fell within 80.0% to 125.0% equivalence limits. The LS mean differences in abiraterone trough plasma concentrations were not statistically significant at any visit. Adverse event frequency was comparable between arms (75.0%, AAFP; 82.8%, OAA). Musculoskeletal events were more common among OAA-treated patients (37.9% vs. 12.5%). CONCLUSION: Therapeutic equivalence between AAFP 500mg daily and OAA 1000mg daily based on serum testosterone levels was confirmed in mCRPC patients. Both agents led to similar PSA-50 response rates. Abiraterone trough levels were similar between treatments. No new safety concerns were observed.

Impact of an alternative steroid on the relative bioavailability and bioequivalence of a novel versus the originator formulation of abiraterone acetate.

PURPOSE: The originator abiraterone acetate (OAA) formulation is used for the treatment of metastatic castration-resistant prostate cancer (mCRPC). This study evaluated the bioavailability and bioequivalence of a novel formulation, abiraterone acetate fine particle (AAFP), versus OAA on a steady-state background of steroids. METHODS: Thirty-seven healthy male subjects were randomized in a crossover design to receive methylprednisolone (4 mg twice daily) or prednisone (5 mg twice daily) for 12 days in Period 1. On Day 11 of Period 1, subjects given methylprednisolone received a single dose of AAFP 500 mg, and subjects given prednisone received a single dose of OAA 1000 mg under fasted conditions. After a 2-week steroid washout period, subjects received the alternate treatments in Period 2. RESULTS: There were no statistical differences regarding area under the curve (AUC) and maximum concentration (C max) between AAFP and OAA. The bioavailability of abiraterone from AAFP versus OAA by geometric mean ratio was AUC0-∞, 95.9% (90% confidence interval [CI] 86.0-106.9); AUC0-t , 99.2% (88.7-110.9); and C max, 116.8% (102.2-133.4). The coefficient of variation (CV) was smaller for AAFP versus OAA (AUC0-∞, CV 44.23 vs. 55.61%; AUC0-t , 45.17 vs. 58.16%; C max, 54.55 vs. 65.65%, respectively). Both treatments were safe and well tolerated. CONCLUSIONS: AAFP plus methylprednisolone provided abiraterone exposure that was comparable to OAA plus prednisone with respect to C max and AUC. Less drug exposure variability was observed with AAFP compared with OAA. Reduced pharmacokinetic variability may positively influence clinical outcomes and warrants further study in mCRPC patients.

Comparison of a Novel Formulation of Abiraterone Acetate vs. the Originator Formulation in Healthy Male Subjects: Two Randomized, Open-Label, Crossover Studies.

BACKGROUND AND OBJECTIVE: Abiraterone acetate is approved for the treatment of metastatic castration-resistant prostate cancer. The originator abiraterone acetate (OAA) formulation is poorly absorbed and exhibits large pharmacokinetic variability in abiraterone exposure. Abiraterone acetate fine particle (AAFP) is a proprietary formulation (using SoluMatrix Fine Particle Technology™) designed to increase the oral bioavailability of abiraterone acetate. Here, we report on two phase I studies in healthy male subjects aged 18-50 years. METHODS: In Study 101, 20 subjects were randomized in a crossover design to single doses of AAFP 100, 200, or 400 mg or OAA 1000 mg taken orally under fasting conditions. Results suggested that AAFP 500 mg would be bioequivalent to OAA 1000 mg in the fasted state. To confirm the bioequivalence hypothesis and to further expand the AAFP dose range, in Study 102, 36 subjects were randomized in a crossover design to single doses of AAFP 125, 500, or 625 mg or OAA 1000 mg. Both studies included a 7-day washout period between administrations. RESULTS: Dose-dependent increases in the area under the plasma concentration-time curve and maximum plasma concentration with AAFP were observed in both studies. The AAFP 500-mg bioavailability relative to OAA 1000 mg measured by the geometric mean ratio for area under the plasma concentration-time curve from time zero to the time of the last quantifiable concentration was 93.4% (90% confidence interval 85.3-102.4), area under the plasma concentration-time curve from time zero to infinity was 91.0% (90% confidence interval 83.3-99.4), and maximum plasma concentration was 99.8% (90% confidence interval 86.3-115.5). Dose proportionality was seen across all AAFP dose levels (100-625 mg). Abiraterone acetate fine particle was found to be safe and well tolerated in this study. CONCLUSION: Abiraterone acetate fine particle 500 mg was demonstrated to be bioequivalent to OAA 1000 mg in healthy volunteers under fasted conditions.

Immunogenicity and long-term efficacy of botulinum toxin type B in the treatment of cervical dystonia: report of 4 prospective, multicenter trials.

OBJECTIVE: Therapeutic botulinum toxins are antigenic proteins with the potential to produce antibodies (Abs). It is, however, unclear whether Abs to Myobloc® (rimabotulinumtoxinB, botulinum toxin type B, BoNT-B) impact the efficacy and safety of BoNT-B treatment of cervical dystonia (CD). The objective was to determine if Abs to BoNT-B impact the efficacy or safety of long-term BoNT-B treatment of CD. METHODS: Four separate prospective clinical trials, with a combined total of 1134 subjects evaluable for immunogenicity over total treatment durations of up to 6+ years, were conducted studying the efficacy, safety, and immunogenicity of BoNT-B treatment of CD. Botulinum toxin type B injections were administered approximately every 3 months. Efficacy was assessed using the Toronto Western Spasmodic Torticollis Rating Scale-Total Score, the Subject Global Assessment, or the Treatment Assessment Scale. The presence of Abs to BoNT-B was assessed using the mouse neutralizing antibody (MNA) assay. Cross-sectional and longitudinal statistical analyses were performed to compare efficacy by MNA status at each time point and over time in Ab-positive individuals before and after seroconversion. Safety was assessed by summarizing adverse events by Ab status. RESULTS: Long-term efficacy was observed with multiple treatments of BoNT-B. Across all 4 studies, there was no correlation between MNA status and rates of clinical response, study withdrawal, or safety profile. CONCLUSIONS: Botulinum toxin type B is effective and safe in the repeat, long-term treatment of CD. The presence of Abs to BoNT-B as detected by the MNA assay does not have any meaningful clinical impact or correlation.

Safety and efficacy of botulinum toxin type B for treatment of sialorrhea in Parkinson's disease: a prospective double-blind trial.

Sialorrhea (drooling) is a common symptom of Parkinson's disease (PD) that can significantly impair a patient's health and quality of life. Fifty-four PD subjects with troublesome sialorrhea were enrolled using a multicenter, randomized, double-blind, sequential-dose escalation design in which subjects received a single intraglandular treatment with botulinum toxin type B (doses of 1,500 Units [0.3 mL]; 2,500 Units [0.5 ml]; or 3,500 Units [0.7 ml]) or placebo. Postinjection, subjects were followed acutely for 4 weeks and long-term for up to 20 weeks. Safety/tolerability, as assessed by adverse events, was the primary outcome measure. Efficacy, as assessed by the Drooling Frequency and Severity Scale and unstimulated salivary flow rate, was secondary. Gastrointestinal-related adverse events occurred more frequently in the active groups versus placebo group (31% vs 7%), with dry mouth being most common (15%). There were no serious adverse events attributed to botulinum toxin type B or discontinuations due to adverse events from treatment. At 4 weeks postinjection, Drooling Frequency and Severity Scale scores significantly improved versus placebo (-1.3 ± 1.3) in a dose-related manner (-2.1 ± 1.2, P = 0.0191; -3.3 ± 1.4, P < 0.0001; -3.5 ± 1.1, P < 0.0001, respectively) and unstimulated salivary flow rates significantly decreased in all active groups versus placebo (P ≤ 0.0009). Furthermore, treated subjects appeared to have more sustained improvement in sialorrhea than placebo subjects. We conclude that intraglandular injection of botulinum toxin type B was safe, tolerable, and efficacious in treating sialorrhea in PD patients. Additional studies are warranted to further confirm the drug's robust efficacy, as well as evaluate its effect with repeated dosing.