Pharmacokinetic and Pharmacodynamic Analysis of Subcutaneous Tocilizumab in Patients With Rheumatoid Arthritis From 2 Randomized, Controlled Trials: SUMMACTA and BREVACTA.

Tocilizumab is a humanized anti-interleukin-6 receptor antibody for treating rheumatoid arthritis. Pharmacokinetic/pharmacodynamic analysis was performed on the 24-week double-blind parts of 2 randomized, controlled trials: SUMMACTA and BREVACTA. SUMMACTA compared subcutaneous tocilizumab 162 mg every week to intravenous tocilizumab 8 mg/kg every 4 weeks, whereas BREVACTA evaluated 162 mg subcutaneous tocilizumab every 2 weeks versus placebo. In addition to noncompartmental analysis, a 2-compartment population pharmacokinetic model, with first-order absorption (for subcutaneous) and linear and Michaelis-Menten elimination was used. Mean observed steady-state predose tocilizumab concentrations in week 24 were 40 and 7.4 µg/mL for subcutaneous every-week and every-2-week dosing, respectively, and 18 µg/mL for intravenous dosing. In the population PK model, body weight was an important covariate affecting clearance and volume of distribution. Mean ± SD population-predicted predose concentration for patients ≥100 kg was 23.0 ± 13.5 µg/mL for subcutaneous tocilizumab every week and 1.0 ± 1.6 µg/mL for every 2 weeks. Efficacy was lowest with subcutaneous every-2-week dosing in patients > 100 kg, reflecting lower exposure. The subcutaneous every-2-week regimen is not recommended for these patients. Pharmacodynamic responses were comparable for the every-week subcutaneous and every-4-week intravenous regimens and less pronounced with the every-2-week subcutaneous regimen. No trend was observed for increased adverse events with increasing tocilizumab exposure. The results of this analysis are consistent with the noninferiority of efficacy of the every-week subcutaneous regimen to the every-4-week intravenous regimen and the superiority of the every-2-week subcutaneous regimen to placebo. These results support the label recommendations for subcutaneous dosing of tocilizumab in rheumatoid arthritis patients.

Clinical efficacy and safety maintained up to 5 years in patients with rheumatoid arthritis treated with tocilizumab in a randomised trial.

OBJECTIVES: To report 5-year efficacy and safety in rheumatoid arthritis (RA) patients with active disease treated with tocilizumab. METHODS: LITHE was a 2-year, randomised, placebo-controlled study of tocilizumab in RA patients (ClinicalTrials.gov, NCT00106535), with an additional 3-year, open-label extension. Patients were randomly assigned to tocilizumab (4 or 8 mg/kg IV) or placebo every 4 weeks + methotrexate. They could receive rescue with tocilizumab from week 16; after week 52, patients could switch to open-label tocilizumab 8 mg/kg. Radiographs were analysed by randomized treatment using the Genant-modified Total Sharp Score (GmTSS). Patients with at least baseline, week 104 and post-week 104 radiographs were included. Clinical and safety data were pooled for all patients who received ≥1 dose of tocilizumab; results are presented from the first tocilizumab dose. RESULTS: 1,149 patients were included with 4,380 patient-years of exposure; 34% received 5 years of treatment. Mean 5-year change in GmTSS revealed greater inhibition of radiographic progression in tocilizumab patients than placebo patients (1.34 vs. 3.02), with the greatest annualised progression rate in year 1. Overall, 53% of tocilizumab and 35% of placebo patients experienced no progression (GmTSS ≤0). Clinical benefit was maintained - determined by ACR response, DAS28-ESR <2.6, EULAR good/moderate response and Boolean remission - as was physical function. The safety profile over 5 years was similar to that over 2 years. CONCLUSIONS: Over 5 years, tocilizumab + MTX inhibited radiographic progression and maintained improvements in signs and symptoms and physical function in MTX-inadequate responders with active disease; no new safety signals occurred.

Efficacy and safety of subcutaneous tocilizumab versus intravenous tocilizumab in combination with traditional DMARDs in patients with RA at week 97 (SUMMACTA).

OBJECTIVES: To evaluate the long-term efficacy and safety of subcutaneous (SC) tocilizumab (TCZ) versus intravenous (IV) TCZ, including switching formulations, in patients with rheumatoid arthritis (RA) and inadequate response to disease-modifying antirheumatic drugs (DMARDs). METHODS: Patients (n=1262) were randomised 1:1 to receive TCZ-SC 162 mg weekly (qw)+placebo-IV every four weeks (q4w) or TCZ-IV 8 mg/kg q4w+placebo-SC qw in combination with DMARD(s). After a 24-week double-blind period, patients receiving TCZ-SC were re-randomised 11:1 to TCZ-SC (n=521) or TCZ-IV (TCZ-SC-IV, n=48), and patients receiving TCZ-IV were re-randomised 2:1 to TCZ-IV (n=372) or TCZ-SC (TCZ-IV-SC; n=186). Maintenance of clinical responses and safety through week 97 were assessed. RESULTS: The proportions of patients who achieved American College of Rheumatology (ACR)20/50/70 responses, Disease Activity Score in 28 joints remission and improvement from baseline in Health Assessment Questionnaire Disability Index ≥0.3 were sustained through week 97 and comparable across arms. TCZ-SC had a comparable safety profile to TCZ-IV through week 97, except that injection site reactions (ISRs) were more common with TCZ-SC. Safety profiles in patients who switched were similar to those in patients who received continuous TCZ-SC or TCZ-IV treatment. The proportion of patients who developed anti-TCZ antibodies remained low across treatment arms. No association between anti-TCZ antibody development and clinical response or adverse events was observed. CONCLUSIONS: The long-term efficacy and safety of TCZ-SC was maintained and comparable to that of TCZ-IV, except for ISRs. Profiles in patients who switched formulations were comparable to those in patients who received TCZ-IV or TCZ-SC. TCZ-SC provides additional treatment options for patients with RA. TRIAL REGISTRATION NUMBER: NCT01194414.

Subcutaneous tocilizumab versus placebo in combination with disease-modifying antirheumatic drugs in patients with rheumatoid arthritis.

OBJECTIVE: The efficacy and safety of subcutaneous tocilizumab (TCZ-SC) versus subcutaneous placebo (PBO-SC) was evaluated in patients with rheumatoid arthritis who had an inadequate response to disease-modifying antirheumatic drugs in the BREVACTA study. METHODS: Patients (n = 656) were randomized 2:1 to receive TCZ-SC 162 mg every other week or PBO-SC every other week for 24 weeks; 20% previously received anti-tumor necrosis factor treatment. Escape therapy with TCZ-SC 162 mg weekly was offered from week 12 for inadequate response. The primary end point was the American College of Rheumatology 20% improvement (ACR20) response at week 24. The key secondary outcomes were radiographic progression and safety. RESULTS: TCZ-SC was superior to PBO-SC for ACR20 response at week 24 (60.9% versus 31.5%; P < 0.0001). All secondary end points showed TCZ-SC to be superior to PBO-SC, including ACR50 and ACR70 response (40% and 20% for TCZ-SC, respectively, and 12% and 5% for PBO-SC, respectively; P < 0.0001 for both) and Disease Activity Score in 28 joints (DAS28) remission (DAS28 <2.6; 32% versus 4% [P < 0.0001]). The mean change in modified Sharp/van der Heijde score was significantly lower in the TCZ-SC group than the PBO-SC group (0.62 versus 1.23; P = 0.0149). Adverse events (AEs) and serious AEs (SAEs) were comparable between the TCZ-SC and PBO-SC groups; 4.6% and 3.7% of patients had at least 1 SAE, respectively, and infection was the most common SAE in 2.1% and 1.8% of patients, respectively. More injection site reactions occurred with TCZ-SC than PBO-SC (7.1% versus 4.1%). No anaphylaxis or serious hypersensitivity reactions occurred. There were 3 deaths in the TCZ-SC group and 0 in the PBO-SC group. CONCLUSION: TCZ-SC every other week had significantly greater efficacy, including ACR end points and inhibition of joint damage, compared with PBO-SC. TCZ-SC was well tolerated and its safety profile was comparable with that of previous intravenous TCZ studies.

Assessment of disease-drug-drug interaction between single-dose tocilizumab and oral contraceptives in women with active rheumatoid arthritis.

OBJECTIVES: The objective of this study was to evaluate the effect of a single intravenous dose of tocilizumab (TCZ) on pharmacokinetics (PK) of oral contraceptive (OC; norethindrone (NE) and ethinyl estradiol (EE)) and on sex hormone levels (progesterone (PG), luteinizing hormone (LH), and follicle-stimulating hormone (FSH)) in subjects with active rheumatoid arthritis (RA) who were on stable doses of methotrexate. METHODS: This was an open-label, nonrandomized, multicenter, two-parallel group, one-sequence crossover study. In Group 1, Cycle 1 was a baseline cycle to determine the PK of OC and levels of sex hormones. At the start of Cycle 2, patients continued to receive OC and single TCZ dosing on Day 1. In Cycle 2, we determined the PK of OC and levels of sex hormones when OC and TCZ were combined. In Cycle 3, we determined the PK of OC and the levels of sex hormones after TCZ treatment was stopped. PK for EE and NE were analyzed serially on Day 7 when maximum TCZ effect on inflammation as indicated by C-reactiv protein (CRP) was expected. Hormone levels (PG, LH and FSH) were measured mid-cycle (cycle Days 12 - 16 and Day 21) during each cycle. Group 2 (healthy subjects) was studied to compare the levels of OC PK exposures with those in each cycle of Group 1 (RA subjects). RESULTS: Levels of PG, LH and FSH were not affected by the combination of TCZ/OC treatment in RA patients studied. No breakthrough bleeding was attributed to the initiation of TCZ treatment in subjects receiving OCs. PK exposures of EE and NE were similar between RA and healthy subjects at baseline and were not affected by single-dose TCZ. Administration of OC with or without a single dose of TCZ was well tolerated. CONCLUSIONS: Data from this study indicated that the PK and sex hormone levels were not affected in RA subjects who had active disease and were on a stable regimen of methotrexate.

A randomised, double-blind, parallel-group study of the safety and efficacy of subcutaneous tocilizumab versus intravenous tocilizumab in combination with traditional disease-modifying antirheumatic drugs in patients with moderate to severe rheumatoid arthritis (SUMMACTA study).

OBJECTIVES: This study compared the efficacy and safety of subcutaneous (SC) versus intravenous (IV) formulations of tocilizumab in patients with rheumatoid arthritis with an inadequate response to disease-modifying antirheumatic drugs (DMARD). METHODS: Patients (n=1262) were randomly assigned to receive tocilizumab-SC 162 mg weekly+placebo-IV every 4 weeks or tocilizumab-IV 8 mg/kg every 4 weeks+placebo-SC weekly in combination with traditional DMARD. The primary outcome was to demonstrate the non-inferiority of tocilizumab-SC to tocilizumab-IV with regard to the proportion of patients in each group achieving an American College of Rheumatology (ACR) 20 response at week 24 using a 12% non-inferiority margin (NIM). Secondary outcomes were disease activity score using 28 joints (DAS28), ACR responses, health assessment questionnaire scores and safety assessments. RESULTS: At week 24, 69.4% (95% CI 65.5 to 73.2) of tocilizumab-SC-treated patients versus 73.4% (95% CI 69.6 to 77.1) of tocilizumab-IV-treated patients achieved an ACR20 response (weighted difference between groups -4.0%, 95% CI -9.2 to 1.2); the 12% NIM was met. ACR50/70 responses, DAS28 and physical function improvements were comparable between the tocilizumab-SC and tocilizumab-IV groups. The safety profiles of tocilizumab-SC and tocilizumab-IV were similar, and the most common adverse event was infection. Injection-site reactions (ISR) occurred more frequently in the tocilizumab-SC group than in the tocilizumab-IV (placebo-SC) group. No anaphylaxis was reported over the 24 weeks. CONCLUSIONS: Tocilizumab-SC 162 mg weekly demonstrated comparable efficacy to tocilizumab-IV 8 mg/kg. The safety profile of tocilizumab-SC is consistent with the known and well-established safety profile of tocilizumab-IV, with the exception of a higher incidence of ISR, which were more common with tocilizumab-SC administration.

Pharmacokinetics and pharmacodynamics of tocilizumab after subcutaneous administration in patients with rheumatoid arthritis.

OBJECTIVES: To investigate the pharmacokinetics, pharmacodynamics, safety and efficacy of subcutaneous tocilizumab 162 mg weekly (QW) or every other week (Q2W) in rheumatoid arthritis patients on methotrexate. METHODS: This was a multicenter, open-label, randomized, parallel group study. Patients were randomly assigned to receive tocilizumab 162 mg subcutaneously QW or Q2W for 12 weeks. Pharmacokinetic and pharmacodynamic measurements were taken from baseline through to treatment end. Efficacy was assessed at baseline and Q4W thereafter. Safety and tolerability were monitored. RESULTS: 29 patients received tocilizumab treatment for 12 weeks. After final QW and Q2W dosing, mean ± SD for Cmax, Cmin and AUC0-168h/0-336h was 39.4 ± 18.1 and 10.7 ± 6.6 µg/ml, 27.9 ± 14.7 and 2.3 ± 3.2 µg/ml and 5,505 ± 2,632 and 2,332 ± 1,696 µg×h/ml. Median tmax was 2 - 3 days. Mean soluble interleukin-6 receptor (sIL-6R) complex concentration increased within 1 week and plateaued (670 ± 211 (QW); 387 ± 194 ng/ml (Q2W)) by final dosing; median C-reactive protein (CRP) levels decreased to below upper limit of normal after first and third doses; mean ± SD (range) reduction in Disease Activity Score using 28 joints at Week 12 was similar between groups (-2.5 ± 1.2 (-4 to -1); -3.1 ± 1.1 (-5 to -2)). Patients experiencing ≥ 1 adverse event were comparable between groups (71% vs. 80%). CONCLUSIONS: Greater tocilizumab exposure and sIL-6R elevation and more rapid CRP level normalization occurred with QW than with Q2W dosing. Both regimens demonstrated clinical benefit and were well tolerated.

Design of the tocilizumab in giant cell arteritis trial.

Overview. The GiACTA trial is a multicenter, randomized, double-blind, and placebo-controlled study designed to test the ability of tocilizumab (TCZ), an interleukin (IL)-6 receptor antagonist, to maintain disease remission in patients with giant cell arteritis (GCA). Design. Approximately 100 centers will enroll 250 patients with active disease. The trial consists of a 52-week blinded treatment phase followed by 104 weeks of open-label extension. Patients will be randomized into one of four groups. Group A (TCZ 162 mg weekly plus a 6-month prednisone-taper); group B (TCZ 162 mg every other week plus a 6-month prednisone-taper); group C (placebo plus a 6-month prednisone-taper); and group D (placebo plus a 12-month prednisone taper). We hypothesize that patients assigned to TCZ in addition to a 6-month prednisone course are more likely to achieve the primary efficacy endpoint of sustained remission (SR) at 52 weeks compared with those assigned to a 6-month prednisone course alone, thus potentially minimizing the long-term adverse effects of corticosteroids. Conclusion. GiACTA will test the hypothesis that interference with IL-6 signaling exerts a beneficial effect on patients with GCA. The objective of this paper is to describe the design of the trial and address major issues related to its development.

Pharmacokinetics and pharmacodynamics of tocilizumab, a humanized anti-interleukin-6 receptor monoclonal antibody, following single-dose administration by subcutaneous and intravenous routes to healthy subjects.

OBJECTIVES: Tocilizumab, a humanized anti-interleukin-6 receptor (IL-6R) monoclonal antibody, given by intravenous (i.v.) infusion every 4 weeks has been approved for treatment of patients with rheumatoid arthritis. The objective of the study was to determine pharmacokinetics (PK) and pharmacodynamics (PD) of tocilizumab including absolute PK and PD bioavailabilities following subcutaneous (s.c.) administration. METHODS: The PK and PD of tocilizumab 162 mg or 81 mg after single s.c. and i.v. administration were evaluated in an open-label, 4-parallel group study involving 48 healthy subjects (n = 12/group). RESULTS: Following single-dose s.c. administration of tocilizumab, area under the serum concentration-time curve (AUC∞) increased by 6.4-fold, and maximum serum concentration (Cmax) increased by 4-fold, as the dose was doubled from 81 mg to 162 mg. Tocilizumab absolute PK bioavailability (AUC∞ ratio (s.c./i.v.)) was higher at 162 mg (48.8%) than at 81 mg (22.7%). Tocilizumab PD bioavailability for soluble IL-6R (sIL-6R) (AUClast ratio (s.c./i.v.)) was 109% at 162 mg and 80.9% at 81 mg. Tocilizumab PD bioavailability for C-reactive protein (CRP) effect was 98.2% (CRP AUC480h ratio) at 162 mg and 80.4% (AUC240h ratio (s.c./i.v.)) at 81 mg. Tocilizumab was well tolerated at both doses after s.c. and i.v. administration. CONCLUSIONS: Tocilizumab absolute PK bioavailability for s.c. vs. i.v. administration was low; however, the PD effects for sIL-6R and CRP levels were comparable after 162-mg s.c. and i.v. administration. Therefore, 162 mg s.c. dose is a comparable dose for 162 mg i.v. dose based on PD bioavailability.

Pharmacokinetics and pharmacodynamics of single subcutaneous doses of tocilizumab administered with or without rHuPH20.

OBJECTIVES: To investigate the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of tocilizumab with and without rHuPH20 (a recombinant human hyaluronidase) in healthy volunteers. METHODS: This was an open-label, single ascending dose study. Subjects were assigned to tocilizumab 162 mg or tocilizumab 162, 324, or 648 mg plus rHuPH20. PK and PD samples were collected after dosing and were estimated with non-compartmental methods. Geometric mean ratio (GMR) for area under the plasma concentration-time curve from zero to infinity (AUC0-∞) and (maximum serum concentration) Cmax with and without rHuPH20 was estimated using one-way analysis of variance. Safety and tolerability were monitored throughout the study. RESULTS: 48 subjects (12/cohort) received a single dose of tocilizumab with or without rHuPH20. For tocilizumab 162 mg, tocilizumab 162 mg/rHuPH20, tocilizumab 324 mg/rHuPH20, and tocilizumab 648 mg/rHuPH20, mean ± SD tocilizumab PK parameters were 2,510 ± 1,060, 2,860 ± 468, 10,800 ± 3,220, and 29,900 ± 5,280 µg×h/ml for AUC0-∞; 11.5 ± 3.7, 16.2 ± 2.8, 43.8 ± 12.4, and 77.8 ± 14.5 µg/ml for Cmax; and 89.1 ± 41.1, 54.0 ± 19.5, 66.0 ± 26.8, and 86.1 ± 50.6 h for tmax, respectively. Coadministration of tocilizumab 162 mg with rHuPH20 resulted in slightly increased exposure: GMR (90% confidence interval) for AUC0-∞, 1.20 (1.00 - 1.44) and Cmax, 1.45 (1.24 - 1.70). Increasing tocilizumab doses resulted in significant deviation from dose proportionality for tocilizumab Cmax (p = 0.0057) and AUC0-∞ (p < 0.0001). Changes in interleukin-6, soluble interleukin- 6 receptor, and C-reactive protein were also dose dependent and similar with and without rHuPH20. CONCLUSIONS: Tocilizumab in combination with rHuPH20 resulted in slightly increased tocilizumab exposure compared with tocilizumab alone, whereas PD markers were comparable. Subcutaneous administration of tocilizumab with rHuPH20 was well tolerated.

Effect of hepatic and renal impairment on the pharmacokinetics of dalcetrapib: altered distribution of the active thiol?

BACKGROUND AND OBJECTIVE: Dalcetrapib, a cholesteryl ester transfer protein (CETP) modulator, is a thioester pro-drug that is rapidly hydrolysed to generate a pharmacologically active thiol. The thiol covalently binds to plasma proteins as mixed disulfides, extensively distributes into plasma lipoprotein fractions, and is principally cleared by metabolism, including extensive first-pass metabolism. Here we report two studies assessing the effects of hepatic and renal impairment on the pharmacokinetics of the thiol and its primary metabolites. METHODS: Adults with hepatic or renal impairment and healthy controls were recruited in two separate non-randomized, open-label studies. Eligible subjects were aged 18-70 years (hepatic impairment study) or 18-75 years (renal impairment study) with a body mass index 18-40 kg/m(2). Healthy controls were matched by age, bodyweight and sex. Each participant received a single 600 mg oral dose of dalcetrapib. Plasma and urine sampling was performed up to 3-4 days post-dalcetrapib administration for analysis of the pharmacokinetics of the thiol and its primary S-methyl and S-glucuronide metabolites. In the renal impairment study, CETP activity and mass, and lipid profiles were also assessed. RESULTS: Twenty-eight subjects were enrolled in the hepatic impairment study (mild or moderate hepatic impairment, n = 8 in each group; controls, n = 12). Thirty-five subjects participated in the renal impairment study (mild, moderate or severe renal impairment, n = 8 in each group; controls, n = 11). In patients with moderate hepatic impairment, the area under the plasma concentration-time curve from time zero to infinity (AUC(∞)) for thiol exposure was increased 34 % (geometric mean ratio [GMR] 1.34, 90 % CI 1.02-1.76), compared with matched controls. Regression analysis revealed a weak inverse relationship between thiol exposure and creatinine clearance (p = 0.0137, r(2) = 17.1 %). In patients with moderate or severe renal impairment, thiol exposures were 62 % (AUC(∞) GMR 1.62, 90 % CI 0.81-3.27) and 81 % (AUC(∞) GMR 1.81, 90 % CI 1.21-2.71) higher, respectively, than matched controls. Exposures of the S-glucuronide and S-methyl metabolites were also higher in hepatic and renal impairment groups. In the renal impairment study, CETP activity was decreased following administration of dalcetrapib, with no clear differences between groups. CONCLUSION: Hepatic and renal impairment both altered dalcetrapib pharmacokinetics and increased thiol exposure, with the extent of the effect dependent on the severity of impairment. The effect of renal impairment may be linked to altered distribution of the thiol, which illustrates the importance of assessing distribution to understand the causes and consequences of altered pharmacokinetics of thiol drugs in patient populations.

Evidence of a drug-drug interaction linked to inhibition of ester hydrolysis by orlistat.

: Orlistat, a lipase inhibitor taken with meals at doses of 60 mg (available over-the-counter) or 120 mg (prescription only) for treatment of obesity, is known to impair the absorption of fat-soluble molecules. Dalcetrapib, a modulator of cholesteryl ester transfer protein activity, is a lipophilic thioester prodrug. Lipase-induced and pancreatin-induced hydrolysis of dalcetrapib in biorelevant media in vitro was very efficiently inhibited by orlistat. Thus, the potential for orlistat to affect the bioavailability of concomitantly administered dalcetrapib was studied in an open-label 2-cohort study in 24 healthy volunteers as follows: single 600-mg doses of dalcetrapib were administered with increasing doses of orlistat (cohort A: 10, 40, 120 mg; cohort B: 20, 60, 120 mg). Exposure to the active form of dalcetrapib was more than 50% lower when taken with orlistat 60 mg or 120 mg than when taken alone. Similar trends were observed with lower orlistat doses (20 mg and 40 mg). Concomitant administration of orlistat also reduced the pharmacodynamic effects of dalcetrapib treatment on cholesteryl ester transfer protein activity. The interaction exceeds that predicted on the basis of dalcetrapib lipophilicity. These findings demonstrate the potential for large interactions between orlistat and esters that undergo de-esterification in the gastrointestinal tract, independent of lipophilicity.

Pharmacokinetic interaction study of ritonavir-boosted saquinavir in combination with rifabutin in healthy subjects.

The effect of multiple doses of rifabutin (150 mg) on the pharmacokinetics of saquinavir-ritonavir (1,000 mg of saquinavir and 100 mg of ritonavir [1,000/100 mg]) twice daily (BID) was assessed in 25 healthy subjects. Rifabutin reduced the area under the plasma drug concentration-time curve from 0 to 12 h postdose (AUC(0-12)), maximum observed concentration of drug in plasma (C(max)), and minimum observed concentration of drug in plasma at the end of the dosing interval (C(min)) for saquinavir by 13%, 15%, and 9%, respectively, for subjects receiving rifabutin (150 mg) every 3 days with saquinavir-ritonavir BID. No effects of rifabutin on ritonavir AUC(0-12), C(max), and C(min) were observed. No adjustment of the saquinavir-ritonavir dose (1,000/100 mg) BID is required when the drugs are administered in combination with rifabutin. The effect of multiple doses of saquinavir-ritonavir on rifabutin pharmacokinetics was evaluated in two groups of healthy subjects. In group 1 (n = 14), rifabutin (150 mg) was coadministered every 3 days with saquinavir-ritonavir BID. The AUC(0-72) and C(max) of the active moiety (rifabutin plus 25-O-desacetyl-rifabutin) increased by 134% and 130%, respectively, compared with administration of rifabutin (150 mg) once daily alone. Rifabutin exposure increased by 53% for AUC(0-72) and by 86% for C(max). In group 3 (n = 13), rifabutin was coadministered every 4 days with saquinavir-ritonavir BID. The AUC(0-96) and C(max) of the active moiety increased by 60% and 111%, respectively, compared to administration of 150 mg of rifabutin once daily alone. The AUC(0-96) of rifabutin was not affected, and C(max) increased by 68%. Monitoring of neutropenia and liver enzyme levels is recommended for patients receiving rifabutin with saquinavir-ritonavir BID.

Effects of intermittent intravenous ibandronate injections on bone quality and micro-architecture in women with postmenopausal osteoporosis: the DIVA study.

In the Dosing IntraVenous Administration (DIVA) study, IV ibandronate injections (15-30 s duration) provided significantly greater gains in bone mineral density than daily oral ibandronate (P<0.001). Single transiliac bone biopsy was performed in a subgroup of women (n=109/1395) from DIVA to assess the impact of ibandronate on newly formed bone and bone remodeling. Patients received ibandronate IV injections 2 mg every 2 months, 3 mg every 3 months or oral ibandronate 2.5 mg daily, plus oral or IV placebo, as appropriate to maintain blinding. Of the 1395 participants from the DIVA study, 122 were enrolled in the substudy. Qualitative histological analysis was performed on all biopsy cores and 89 cores were considered to be evaluable for quantitative histomorphometry. Following 2 years of ibandronate treatment, trabecular bone maintained its normal lamellar structure with no evidence of woven bone, marrow fibrosis, cellular toxicity, or other qualitative abnormalities. Primary mineralization of new bone remained normal, as indicated by the slightly lower osteoid thickness and osteoid volume, with normal mineral apposition rate compared to healthy, postmenopausal women. Mineralizing surface, osteoid surface, activation frequency and bone formation rate were decreased in all ibandronate-treated groups compared with values from healthy, postmenopausal women. Specifically, the bone formation rate (BFR/BV and BFR/BS) was approximately 5 times lower in the ibandronate-treated (3 mg) group than in healthy, postmenopausal women. Histomorphometric analysis of transiliac bone biopsies demonstrated normal micro-structure of newly formed bone with normal mineralization and reduced remodeling after oral or IV ibandronate.

A randomized, controlled study evaluating an induction treatment strategy in which enfuvirtide was added to an oral, highly active antiretroviral therapy regimen in treatment-experienced patients: the INTENSE study.

OBJECTIVES: The aim of the study was to compare the efficacy and safety of induction with the addition of enfuvirtide to a newly designed oral, highly active antiretroviral therapy (HAART) regimen versus HAART alone followed by a maintenance phase wherein participants were randomized to either continue/discontinue enfuvirtide while maintaining HAART or continue HAART alone (NCT00487188). METHODS: Participants with HIV-1 RNA >/=1000 copies/mL, CD4 count >/=200 cells/mm(3) and genotype sensitivity score >/=2 (excluding enfuvirtide) were randomized 2:1 to enfuvirtide+HAART or HAART alone and assessed every 4 weeks. Participants achieving <50 copies/mL on two consecutive visits by week 24 entered a maintenance phase wherein those receiving enfuvirtide+HAART underwent another randomization 1:1 to maintain enfuvirtide+HAART or discontinue enfuvirtide; those receiving HAART alone continued their regimen. Virological and immunological endpoints were analysed at weeks 24 and 48. RESULTS: At 24 weeks, 20/31 (65%) participants in the enfuvirtide+HAART arm versus 8/16 (50%) participants in the HAART arm achieved <50 copies/mL. Median time to achieving <50 copies/mL was 57 versus 141 days in the enfuvirtide+HAART and HAART arms (P = 0.048). Withdrawals were similar between groups. In the maintenance phase, at 48 weeks, 14/19 (74%) in the original enfuvirtide+HAART arm (regardless of second randomization) versus 4/8 (50%) in the HAART arm had <50 copies/mL. During maintenance, there were two virological failures in the enfuvirtide+HAART continuation arm, one in the enfuvirtide discontinuation arm and none in the HAART arm. CONCLUSIONS: Although limited by small participant numbers, these results suggest that treatment with enfuvirtide added to HAART may be an option for many patients.

Efficacy and safety of 48 weeks of enfuvirtide 180 mg once-daily dosing versus 90 mg twice-daily dosing in HIV-infected patients.

PURPOSE: To evaluate the safety and antiviral activity of once-daily (qd) enfuvirtide (ENF) compared with twice daily (bid) ENF. METHOD: T20-401 was a phase 2, open-label, randomized, 48-week pilot study comparing ENF 180 mg qd versus ENF 90 mg bid, added to an optimized background (OB) regimen. Patients were randomized 1:1 to receive ENF 180 mg qd given as two 90-mg injections (n = 30) or one 90-mg injection bid (n = 31), plus OB. The primary efficacy endpoint was the proportion of patients achieving a HIV-1 RNA viral load <400 copies/mL. Adherence, pharmacokinetics, safety, and tolerability parameters, including injection site reactions (ISRs), were compared between treatment arms. RESULTS: At Week 48, 23.3% of patients on once daily versus 22.6% on twice daily (p = .969) reached <400 copies/mL and 13.3% and 22.6% (p = .323), respectively, reached <50 copies/mL. The proportion reporting 1 adverse event or ISRs was comparable between arms, despite an increased incidence of grade 4 erythema (13% vs. 0%), induration (33% vs. 12%), and ecchymosis (7% vs. 0%) on twice daily versus once daily. ENF adherence (95% of prescribed doses) was higher on once daily (80.0%) versus twice daily (58.1%). CONCLUSION: The antiviral efficacy, safety, and tolerability of 180 mg ENF qd appeared comparable with that of 90 mg ENF bid at Week 48, although the study was not powered to demonstrate the noninferiority of once daily versus twice daily.

Adherence to enfuvirtide and its impact on treatment efficacy.

High adherence rates to antiretroviral (ARV) therapy are associated with increased durability of viral suppression and decreased rates of drug resistance. The requirement of twice-daily subcutaneous self-administration of enfuvirtide (ENF) has raised concerns about adherence. This study assesses adherence to ENF and an optimized background (OB) of ARVs and its impact on virological and immunological responses during the TORO trials. Eighty-eight percent of patients in the OB arm reported > or = 85% adherence versus 87% of patients in the ENF + OB arm. Higher overall adherence was associated with improved virological and immunological response in both treatment arms at 48 weeks. In patients with > or = 85% adherence, 33% of patients in the ENF + OB arm achieved HIV-1 RNA < 400 copies/ml, versus 13% in the OB arm (p < 0.0001). Similarly, patients with > or = 85% adherence in the ENF + OB arm achieved a mean increase in CD4 cell count of 104 cells/mm(3) compared with 58 cells/mm(3) for patients in the OB arm (p < 0.001). None of the demographic factors explored (age, gender, race) or baseline characteristics (CD4 count, viral load, or baseline sensitivity score) was significant in predicting adherence to ENF when analyzed by multiple regression. Importantly, a history of intravenous drug use (IDU) was not associated with a significant decrease in adherence (mean adherence for IDU 96% versus mean adherence for non-IDU 96%; p = 0.825). Adherence was high in patients receiving the self-injectable ARV enfuvirtide. In addition, the inclusion of ENF did not negatively impact adherence to the ARV regimen as a whole.

Enfuvirtide does not require dose adjustment in patients with chronic kidney failure: results of a pharmacokinetic study of enfuvirtide in HIV-1-infected patients with impaired kidney function.

OBJECTIVE: The aim of this study was to examine the influence of kidney disease and hemodialysis on the pharmacokinetics ofenfuvirtide. DESIGN: An open-label, multicenter, parallel group study of HIV-1-infected patients with varying degrees of kidney dysfunction. METHODS: A 90-mg dose of enfuvirtide was administered by subcutaneous injection to 3 groups of patients: group A, patients with normal kidney function; group B, patients with chronic kidney disease; and group C, patients with end-stage renal disease (ESRD) requiring dialysis. Patients with ESRD requiring dialysis received the 90-mg dose of enfuvirtide on 2 separate occasions; a dialysis day and a nondialysis day. After each dose, a full 48-hour pharmacokinetic profile was collected and pharmacokinetic parameters were estimated using model-independent techniques. RESULTS: Enfuvirtide area under the curve (AUCinfinity) and maximum observed enfuvirtide plasma concentration (Cmax) for patients with normal kidney function (group A) was 49.6 microg h/mL and 3.79 microg/mL, respectively. Patients with chronic kidney disease (group B) had higher AUCinfinity (80.3 microg h/mL) and Cmax (5.72 microg/mL), which was similar to patients with ESRD (group C) on both nondialysis days (AUCinfinity 71.1 microg h/mL; Cmax 5.34 microg/mL) and dialysis days (AUCinfinity 66.9 microg h/mL; Cmax 6.31 microg/mL). An average of< 13% of enfuvirtide was removed during the dialysis procedure. The incidence of adverse events was comparable for all study groups. CONCLUSION: Enfuvirtide exposure observed in patients with ESRD requiring dialysis or chronic kidney disease was slightly higher than in patients with normal kidney function and similar to historical Cmax and AUC values from studies in patients with normal kidney function. Thus, enfuvirtide does not require dosage adjustment in patients with impaired kidney function.

Switching from a toxicity-causing antiretroviral to enfuvirtide in patients with HIV: the SWITCH TOX study.

PURPOSE: Treatment-related toxicities frequently limit antiretroviral therapy for patients with HIV-1 infection. This study evaluated the changes in treatment-limiting toxicities when the primary toxicity-causing agent was replaced with enfuvirtide. METHOD: Adult patients with HIV-1 infection (N = 91) with antiretroviral treatment-limiting toxicities were enrolled in this multicenter, open-label, single-arm, 24-week study. Enfuvirtide 90 mg bid was administered instead of a single toxicity-causing component of the previous antiretroviral regimen. Changes in severity of antiretroviral toxicity, safety, tolerability, and maintenance of efficacy of the enfuvirtide regimen were evaluated at baseline and at 4, 8, 12, and 24 weeks. RESULTS: Eighty-four percent of participants completed the study. Injection site reactions with enfuvirtide caused premature withdrawal in 5 participants (5%); a further 10 participants (11%) also withdrew early. Overall antiretroviral-related, treatment-limiting toxicities improved or resolved in 53% of participants switching to enfuvirtide, remained unchanged in 43%, and worsened in 3%. At Week 24, 66% of participants (60/91; intent-to-treat population) maintained or improved their viral load category and 73% of participants (66/91) maintained or improved their CD4 cell counts. CONCLUSION: Replacing a toxicity-causing antiretroviral with enfuvirtide may reduce toxicity without compromising the efficacy of different antiretroviral regimens.

Safety and efficacy of enfuvirtide for 48 weeks as part of an optimized antiretroviral regimen in pediatric human immunodeficiency virus 1-infected patients.

BACKGROUND: Enfuvirtide is the only entry inhibitor approved for the treatment of human immunodeficiency virus (HIV)-1 infection. It is approved for use in adults and dosage recommendations exist for children aged 6 years or older. METHODS: T20-310 was a multicenter, open-label, nonrandomized, noncomparative study of the safety and efficacy of 2.0 mg/kg (maximum 90 mg) twice-daily subcutaneous enfuvirtide for 48 weeks in 52 treatment-experienced, HIV-1-infected pediatric patients (3-16 years) receiving optimized background therapy. RESULTS: Enfuvirtide was generally well tolerated, and no new patterns of adverse events compared with adults were observed. Mild-to-moderate injection-site reactions were the most common adverse event. Of those participants on treatment for 48 weeks, the median change from baseline in HIV-1 RNA was -1.17 log10 copies/mL (n = 32), and there was a median CD4 change of +106 (n = 25) cells/mm3 and +4.7 CD4%. Seventeen (32.7%) patients achieved a viral load decrease of > or =1 log10 copies/mL and 11 (21.2%) achieved HIV-1 RNA <400 copies/mL. Virologic and immunologic treatment responses were substantially better for children (<11 years) than adolescents. Steady-state mean enfuvirtide C(trough) levels were stable during 24 weeks with no differences between children and adolescents. CONCLUSIONS: Enfuvirtide is an effective treatment for HIV-1 infection in children and adolescents receiving optimized background therapy and has a favorable safety profile. Efficacy in adolescents was inferior; probably related to unique adherence challenges. The long-term safety and efficacy of enfuvirtide in pediatric patients is comparable to that observed in adults.