Subcutaneous Administration of Monoclonal Antibodies: Pharmacology, Delivery, Immunogenicity, and Learnings From Applications to Clinical Development

Subcutaneous (s.c.) administration of monoclonal antibodies (mAbs) can reduce treatment burden for patients and healthcare systems compared with intravenous (i.v.) infusion through shorter administration times, made possible by convenient, patient-centric devices. A deeper understanding of clinical pharmacology principles related to efficacy and safety of s.c.-administered mAbs over the past decade has streamlined s.c. product development. This review presents learnings from key constituents of the s.c. mAb development pathway, including pharmacology, administration variables, immunogenicity, and delivery devices. Restricted mAb transportation through the hypodermis explains their incomplete absorption at a relatively slow rate (pharmacokinetic (PK)) and may impact mAb-cellular interactions and/or onset and magnitude of physiological responses (pharmacodynamic). Injection volumes, formulation, rate and site of injection, and needle attributes may affect PKs and the occurrence/severity of adverse events like injection-site reactions or pain, with important consequences for treatment adherence. A review of immunogenicity data for numerous compounds reveals that incidence of anti-drug antibodies (ADAs) is generally comparable across i.v. and s.c. routes, and complementary factors including response magnitude (ADA titer), persistence over time, and neutralizing antibody presence are needed to assess clinical impact. Finally, four case studies showcase how s.c. biologics have been clinically developed: (i) by implementation of i.v./s.c. bridging strategies to streamline PD-1/PD-L1 inhibitor development, (ii) through co-development with i.v. presentations for anti-severe acute respiratory syndrome-coronavirus 2 antibodies to support rapid deployment of both formulations, (iii) as the lead route for bispecific T cell engagers (BTCEs) to mitigate BTCE-mediated cytokine release syndrome, and (iv) for pediatric patients in the case of dupilumab.

Dupilumab Safety and Efficacy in a Phase III Open-Label Extension Trial in Children 6-11 Years of Age with Severe Atopic Dermatitis

BACKGROUND

For children aged 6-11 years with uncontrolled severe atopic dermatitis (AD), 16 weeks of treatment with dupilumab resulted in substantial clinical benefit compared with placebo with an acceptable safety profile. However, longer-term safety and efficacy data are important to inform longitudinal AD management.

OBJECTIVES

This analysis of data from an open-label extension study (LIBERTY AD PED-OLE, NCT02612454) reports the long-term safety, efficacy, and pharmacokinetics of dupilumab in children with severe AD who had participated in the pivotal dupilumab LIBERTY AD PEDS study (NCT03345914).

METHODS

Enrolled patients initially received subcutaneous dupilumab 300 mg every 4 weeks (q4w). The q4w regimen could be uptitrated to dupilumab dose regimens of 200 or 300 mg every 2 weeks (q2w; for body weight < 60 or ≥ 60 kg, respectively) for patients who did not achieve an Investigator's Global Assessment (IGA) score of 0/1 (clear/almost clear skin) at week 16, or prior to week 16 as rescue treatment. Additional patients were uptitrated to a weight-tiered q2w regimen following a protocol amendment. Patients who maintained an IGA score of 0/1 continuously for a 12-week period after week 40 discontinued dupilumab. They were monitored for relapse and were reinitiated on dupilumab if required.

RESULTS

Data for 321 patients (mean age 8.6 years) were analyzed, 254 (79%) of whom had completed the scheduled 52-week visit at the database lock. Most treatment-emergent adverse events were mild/moderate. By week 52, 41% of patients achieved an IGA score of 0/1, and 97%, 82%, and 50%, respectively, had at least a 50%, 75%, and 90% improvement from the parent study baseline in Eczema Area and Severity Index (EASI). By week 52, 29% of patients in the overall population had clear/almost clear skin sustained for 12 weeks and had stopped medication; of these, 40% relapsed and were subsequently reinitiated on treatment, with a mean time to reinitiation of 13.5 (standard deviation 5.2) weeks. Following reinitiation of dupilumab, 41% of the patients with evaluable data at the time of database lock had regained an IGA 0/1 clinical response.

CONCLUSIONS

Consistent with results seen in adults and adolescents, long-term treatment with dupilumab in children aged 6-11 years with severe AD showed an acceptable safety profile and incremental clinical benefit. A substantial proportion of children who stopped dupilumab treatment after achieving clear/almost clear skin subsequently experienced disease recurrence, and required reinitiation of dupilumab, suggesting that continuous treatment may be necessary for maintenance of clinical benefit.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier NCT02612454.

Integrated Exposure-Response of Dupilumab in Children, Adolescents, and Adults With Atopic Dermatitis Using Categorical and Continuous Efficacy Assessments: A Population Analysis

BACKGROUND

While the majority of patients with atopic dermatitis (AD) achieve disease control with dupilumab treatment, there is variability in which patients achieve clear disease. The predictors of these responses are currently unclear. Integrated models were developed to evaluate the exposure-response (E-R) relationship of dupilumab in children, adolescents, and adults with AD.

METHODS

Data from six Phase II and III clinical studies were pooled (2,366 adults [> 18 years], 243 adolescents [≥ 12 to < 18 years] and 359 children [≥ 6 to < 12 years]) for model development. Efficacy was assessed using the Eczema Area and Severity Index (EASI) and Investigator's Global Assessment (IGA). Indirect response models were applied to link measures of efficacy and functional serum dupilumab concentrations. The covariates on individual placebo-corrected response were assessed. Clinical trial scenarios were simulated to compare E-R relationships across age groups. Safety was not explored.

RESULTS

After correcting for differences in placebo response and dupilumab exposure: 1) older age, higher body weight, lower baseline thymus and activation-regulated chemokine, and Asian race were associated with slightly lower EASI response, and no clear covariates were identified on IGA response; 2) clinical trial simulations generally showed slightly higher response at a given dupilumab concentration in children compared to adults and adolescents with severe and moderate AD.

CONCLUSIONS

The collectively tested covariates explain some of the variability in dupilumab response in patients with AD. Patients in all age groups showed adequate response to dupilumab; however, children showed slightly higher drug effects compared to adults and adolescents at equivalent concentrations.

Characterizing complex and competing drug-drug interactions between the antiviral regimen of glecaprevir and pibrentasvir with rifampin or carbamazepine

The fixed-dose combination of the direct acting antivirals glecaprevir (GLE) and pibrentasvir (PIB) is an oral, once-daily treatment for all six major genotypes of chronic hepatitis C virus infection. A single and multiple-dose rifampin study (N = 12) and a carbamazepine study (N = 12) were conducted in healthy subjects to evaluate the effects of CYP3A/P-gp induction and OATP inhibition on the pharmacokinetics of GLE and PIB. In study 1, GLE 300 mg + PIB 120 mg was administered as a single dose either alone, after single and multiple daily doses of rifampin 600 mg, or 24 h after the last rifampin dose. In study 2, GLE 300 mg + PIB 120 mg was administered as a single dose either alone or after multiple doses of carbamazepine 200 mg. Relative to GLE + PIB alone, exposure of GLE was significantly increased by the first co-administered rifampin dose due to OATP inhibition, significantly decreased 24 h after the last rifampin dose due to CYP3A/P-gp induction, and slightly increased when co-administered with steady-state rifampin due to a combination of inhibition and induction forces. Exposure of PIB was not affected when co-administered with the first rifampin dose but was significantly decreased with steady-state rifampin co-administration, or 24 h after the last rifampin dose due to P-gp induction. Carbamazepine significantly decreased GLE and PIB exposure, mainly attributed to P-gp induction. The regimens tested were generally well-tolerated by the subjects and no new safety issues were identified.

Dupilumab in Adults and Adolescents with Eosinophilic Esophagitis

BACKGROUND

Dupilumab, a fully human monoclonal antibody, blocks interleukin-4 and interleukin-13 signaling, which have key roles in eosinophilic esophagitis.

METHODS

We conducted a three-part, phase 3 trial in which patients 12 years of age or older underwent randomization in a 1:1 ratio to receive subcutaneous dupilumab at a weekly dose of 300 mg or placebo (Part A) or in a 1:1:1 ratio to receive 300 mg of dupilumab either weekly or every 2 weeks or weekly placebo (Part B) up to week 24. Eligible patients who completed Part A or Part B continued the trial in Part C, in which those who completed Part A received dupilumab at a weekly dose of 300 mg up to week 52 (the Part A-C group); Part C that included the eligible patients from Part B is ongoing. The two primary end points at week 24 were histologic remission (≤6 eosinophils per high-power field) and the change from baseline in the Dysphagia Symptom Questionnaire (DSQ) score (range, 0 to 84, with higher values indicating more frequent or more severe dysphagia).

RESULTS

In Part A, histologic remission occurred in 25 of 42 patients (60%) who received weekly dupilumab and in 2 of 39 patients (5%) who received placebo (difference, 55 percentage points; 95% confidence interval [CI], 40 to 71; P<0.001). In Part B, histologic remission occurred in 47 of 80 patients (59%) with weekly dupilumab, in 49 of 81 patients (60%) with dupilumab every 2 weeks, and in 5 of 79 patients (6%) with placebo (difference between weekly dupilumab and placebo, 54 percentage points; 95% CI, 41 to 66 [P<0.001]; difference between dupilumab every 2 weeks and placebo, 56 percentage points; 95% CI, 43 to 69 [not significant per hierarchical testing]). The mean (±SD) DSQ scores at baseline were 33.6±12.41 in Part A and 36.7±11.22 in Part B; the scores improved with weekly dupilumab as compared with placebo, with differences of -12.32 (95% CI, -19.11 to -5.54) in Part A and -9.92 (95% CI, -14.81 to -5.02) in Part B (both P<0.001) but not with dupilumab every 2 weeks (difference in Part B, -0.51; 95% CI, -5.42 to 4.41). Serious adverse events occurred in 9 patients during the Part A or B treatment period (in 7 who received weekly dupilumab, 1 who received dupilumab every 2 weeks, and 1 who received placebo) and in 1 patient in the Part A-C group during the Part C treatment period who received placebo in Part A and weekly dupilumab in Part C.

CONCLUSIONS

Among patients with eosinophilic esophagitis, subcutaneous dupilumab administered weekly improved histologic outcomes and alleviated symptoms of the disease. (Funded by Sanofi and Regeneron Pharmaceuticals; ClinicalTrials.gov number, NCT03633617.).

Dupilumab in children aged 6 months to younger than 6 years with uncontrolled atopic dermatitis: a randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

Current systemic treatments for children younger than 6 years with moderate-to-severe atopic dermatitis that is uncontrolled with topical therapies might have suboptimal efficacy and safety. Dupilumab is approved for older children and adults with atopic dermatitis and for other type 2 inflammatory conditions. We aimed to evaluate efficacy and safety of dupilumab with concomitant low-potency topical corticosteroids in children aged 6 months to younger than 6 years with moderate-to-severe atopic dermatitis.

METHODS

This randomised, double-blind, placebo-controlled, parallel-group, phase 3 trial was conducted in 31 hospitals, clinics, and academic institutions in Europe and North America. Eligible patients were aged 6 months to younger than 6 years, with moderate-to-severe atopic dermatitis (Investigator's Global Assessment [IGA] score 3-4) diagnosed according to consensus criteria of the American Academy of Dermatology, and an inadequate response to topical corticosteroids. Patients were randomly assigned (1:1) to subcutaneous placebo or dupilumab (bodyweight ≥5 kg to <15 kg: 200 mg; bodyweight ≥15 kg to <30 kg: 300 mg) every 4 weeks plus low-potency topical corticosteroids (hydrocortisone acetate 1% cream) for 16 weeks. Randomisation was stratified by age, baseline bodyweight, and region. Patient allocation was done via a central interactive web response system, and treatment allocation was masked. The primary endpoint at week 16 was the proportion of patients with IGA score 0-1 (clear or almost clear skin). The key secondary endpoint (coprimary endpoint for the EU and EU reference market) at week 16 was the proportion of patients with at least a 75% improvement from baseline in Eczema Area and Severity Index (EASI-75). Primary analyses were done in the full analysis set (ie, all randomly assigned patients, as randomly assigned) and safety analyses were done in all patients who received any study drug. This study was registered with ClinicalTrials.gov, NCT03346434.

FINDINGS

Between June 30, 2020, and Feb 12, 2021, 197 patients were screened for eligibility, 162 of whom were randomly assigned to receive dupilumab (n=83) or placebo (n=79) plus topical corticosteroids. At week 16, significantly more patients in the dupilumab group than in the placebo group had IGA 0-1 (23 [28%] vs three [4%], difference 24% [95% CI 13-34]; p<0·0001) and EASI-75 (44 [53%] vs eight [11%], difference 42% [95% CI 29-55]; p<0·0001). Overall prevalence of adverse events was similar in the dupilumab group (53 [64%] of 83 patients) and placebo group (58 [74%] of 78 patients). Conjunctivitis incidence was higher in the dupilumab group (four [5%]) than the placebo group (none). No dupilumab-related adverse events were serious or led to treatment discontinuation.

INTERPRETATION

Dupilumab significantly improved atopic dermatitis signs and symptoms versus placebo in children younger than 6 years. Dupilumab was well tolerated and showed an acceptable safety profile, similar to results in older children and adults.

FUNDING

Sanofi and Regeneron Pharmaceuticals.

Long-Term Efficacy and Safety of Dupilumab in Adolescents with Moderate-to-Severe Atopic Dermatitis: Results Through Week 52 from a Phase III Open-Label Extension Trial (LIBERTY AD PED-OLE)

Background

For adolescent patients (aged ≥ 12 to < 18 years) with uncontrolled moderate-to-severe atopic dermatitis (AD), 16 weeks of treatment with dupilumab resulted in substantial clinical benefit compared with placebo, with an acceptable safety profile. However, long-term data on the approved dose regimens of dupilumab in adolescents with AD are lacking.

Objectives

This open-label extension study (LIBERTY AD PED-OLE, NCT02612454) reports the long-term safety, efficacy, and pharmacokinetics of dupilumab in adolescents with moderate-to-severe AD who had participated in dupilumab parent trials.

Methods

Patients enrolled under the original study protocol received subcutaneous dupilumab according to a weight-based regimen (2 or 4 mg/kg every week). Following protocol amendment, patients were switched to subcutaneous dupilumab 300 mg every 4 weeks (q4w) irrespective of weight, and newly enrolled patients were started on dupilumab 300 mg q4w. Patients with an inadequate clinical response (Investigator’s Global Assessment [IGA] score of 0/1 was not reached) to the q4w regimen could be uptitrated to the approved dupilumab dose regimens of 200 or 300 mg every 2 weeks (body weight < 60 or ≥ 60 kg, respectively). Patients whose IGA score of 0/1 was maintained continuously for a 12-week period after week 40 were discontinued from dupilumab, monitored for relapse, and re-initiated on dupilumab if required.

Results

Data for 294 patients (mean age 14.7 years) were analyzed, 102 (34.7%) of whom had completed the 52-week visit at the database lock. The dupilumab long-term safety profile was comparable to that seen in adults and consistent with the known safety profile. Most treatment-emergent adverse events were mild/moderate. By week 52, 42.7% of patients had an IGA score of 0/1 (clear/almost clear), and 93.1%, 81.2%, and 56.4%, respectively, had at least a 50%, 75%, or 90% improvement in Eczema Area and Severity Index (EASI). Most (70.9%) patients required uptitration to the approved dupilumab dose regimen. The proportions of uptitrated patients with an IGA score of 0/1 or 75% improvement in EASI increased over time, reaching 35.7% and 51.9%, respectively, 48 weeks after the first uptitration visit. By week 52, 29.4% of patients had clear/almost clear skin sustained for 12 weeks and had stopped medication; 56.7% relapsed and were subsequently re-initiated on treatment, with a mean time to re-initiation of 17.5 (± standard deviation 17.3) weeks.

Conclusions

Consistent with results seen with short-term treatment, long-term treatment with dupilumab showed an acceptable safety profile while providing incremental clinical benefit with continued treatment over time. The high proportion of patients who needed uptitration because of inadequate response to q4w dosing supports the q2w dose regimen as optimal for this age group. Finally, the majority of patients who stopped medication after having clear/almost clear skin sustained over 12 weeks experienced disease recurrence, suggesting the need for continued dupilumab dosing to maintain efficacy.

Trial Registration

ClinicalTrials.gov Identifiers: NCT02612454, NCT02407756, NCT03054428, and NCT03050151.

Infographic

Pharmacokinetics of Subcutaneous Dupilumab Injection With an Autoinjector Device or Prefilled Syringe

Dupilumab, a human monoclonal antibody against interleukin‐4 receptor alpha, has demonstrated efficacy and an acceptable safety profile in adult and pediatric patients with moderate‐to‐severe atopic dermatitis (AD) and other type 2 inflammatory diseases. Dupilumab is available in 200‐ and 300‐mg strengths as a prefilled syringe with a needle shield (PFS‐S), and more recently as an autoinjector (AI) device. This study was designed to assess the pharmacokinetic (PK) comparability of a single subcutaneous (SC) dose of dupilumab 200 mg, delivered by 2 different devices, AI (test) versus PFS‐S (reference). A total of 130 healthy male and female participants were enrolled in this phase 1 parallel design study, with 128 evaluable for PK. Following dupilumab 200‐mg SC injection, dupilumab exposure in serum was similar for both AI and PFS‐S. The geometric mean ratios of PK parameters with 90% confidence intervals were 1.08 (0.97‐1.21) for maximum serum concentration (C_max) and 1.11 (0.96‐1.28) for area under the serum concentration–time curve until the last quantifiable concentration (AUC_last). Dupilumab administration by both devices was well tolerated, and there were no serious adverse events, or severe treatment‐emergent adverse events experienced during the study. Overall, exposure to dupilumab 200 mg was comparable when administered via the AI or PFS‐S devices in healthy male and female study participants.

The Posology of Dupilumab in Pediatric Patients With Atopic Dermatitis

Dupilumab demonstrated efficacy with an acceptable safety profile in two randomized, double-blind, placebo-controlled, parallel-group, phase III trials in adolescents (12-17 years; LIBERTY AD ADOL) and children (6-11 years; LIBERTY AD PEDS) with atopic dermatitis (AD) treated for 16 weeks. Here, we present the pharmacokinetic profiles and exposure-response (E-R) relationships of dupilumab that guided the posology in these populations. A total of 251 adolescent patients with moderate-to-severe AD were randomized to subcutaneous dupilumab monotherapy every 2 weeks (q2w; 200 mg q2w, baseline weight < 60 kg; 300 mg q2w, ≥ 60 kg), dupilumab 300 mg every 4 weeks (q4w; non-weight tiered), or placebo; 367 children with severe AD were randomized to dupilumab q2w (100 mg q2w, baseline weight < 30 kg; 200 mg q2w, ≥ 30 kg), dupilumab 300 mg q4w, or placebo. Children received concomitant topical corticosteroids in addition to dupilumab, and loading doses were administered at the start of therapy. Mean dupilumab trough concentrations at week 16 for weight subcategories in each dosing regimen were compared with adult exposures for the approved dupilumab 300 mg q2w regimen. Positive E-R relationships were demonstrated between dupilumab trough concentrations and AD outcome measures across patient populations and regimens; no relationship was observed with treatment-emergent conjunctivitis. Based on these analyses, a weight-tiered posology was proposed for adolescents (200/300 mg q2w in patients 30-< 60 kg/≥ 60 kg) and children (300 mg q4w in patients 15-< 30 kg, 200 mg q2w in patients 30-< 60 kg) with moderate-to-severe AD.

Pharmacokinetics and pharmacodynamics of itepekimab in healthy adults and patients with asthma: Phase I first-in-human and first-in-patient trials

Itepekimab is a monoclonal antibody that targets interleukin (IL‐33) and has been shown to reduce airway inflammation and associated tissue damage in preclinical studies. We assessed the safety, tolerability, pharmacokinetics (PKs), and pharmacodynamic profiles of single‐ascending and multiple‐ascending doses of itepekimab in two randomized, double‐blind, placebo‐controlled phase I studies. Healthy adults (N = 40) were randomized to the single‐dose study and patients with moderate asthma (N = 23) to the multiple‐dose study. Itepekimab was administered intravenously (0.3, 1, 3, or 10 mg/kg infusion) or subcutaneously (150 mg) in the single‐dose study and subcutaneously (75 or 150 mg weekly for 4 weeks) in the multiple‐dose study. Itepekimab exhibited linear PKs across studies and dose‐proportional increases in mean maximum concentration in serum and area under the concentration–time curve following single intravenous or multiple subcutaneous doses. Itepekimab demonstrated mean subcutaneous bioavailability of 59–73% and a long terminal half‐life (30.0–31.6 days). IL‐33 concentrations in most healthy participants and patients with asthma were undetectable at baseline. Following administration of itepekimab in both studies, total IL‐33 concentrations increased and blood eosinophils decreased, both with durable effect. Itepekimab was well‐tolerated in both studies with no detection of treatment‐emergent anti‐drug antibody responses.

Effects of Rovalpituzumab Tesirine on Ventricular Repolarization in Patients With Small-Cell Lung Cancer

Small cell lung cancer (SCLC) is a leading cause of cancer death worldwide, with few treatment options. Rovalpituzumab tesirine (Rova‐T) is an antibody‐drug conjugate that targets delta‐like 3 on SCLC cells to deliver a cytotoxic payload directly to tumor cells. In this study, the cardiac safety profile of Rova‐T was assessed by evaluating changes in QT interval, electrocardiogram (ECG) waveform, heart rate, and proarrhythmic adverse events (AEs) after treatment with Rova‐T in patients with previously treated extensive‐stage SCLC. Patients underwent ECG monitoring for 2 weeks after each of 2 i.v. infusions of 0.3 mg/kg Rova‐T over 30 minutes, administered 6 weeks apart. Forty‐six patients received at least one dose of Rova‐T. At the geometric mean Rova‐T maximum serum concentration of 7,940 ng/mL, ECG monitoring showed no significant changes in the Fridericia‐corrected QT (QTcF) interval; the upper limit of the 2‐sided 90% confidence interval did not exceed 10 msec for any time point. There were no clinically significant changes in QRS or PR intervals, ECG waveforms, or heart rate after Rova‐T administration. All patients experienced a treatment‐emergent AE (TEAE); 78% had a grade ≥ 3 TEAE, 59% had a serious TEAE, and 41% had a cardiac‐related TEAE. The TEAEs that might signal proarrhythmia tendencies were uncommon. Confirmed partial responses were observed in 24% of patients. Based on the evaluation of ECG data collected in this study from patients treated with Rova‐T at 0.3 mg/kg i.v. administered every 6 weeks, a QTcF effect of clinical concern can be excluded.

A phase 2, open-label study of single-dose dupilumab in children aged 6 months to <6 years with severe uncontrolled atopic dermatitis: pharmacokinetics, safety and efficacy

BACKGROUND

Dupilumab has demonstrated efficacy and acceptable safety in adults and children (aged 6-17 years) with moderate-to-severe atopic dermatitis (AD), but effective systemic therapy with a favorable risk-benefit profile in younger children remains a significant unmet need.

OBJECTIVES

To determine the pharmacokinetics, safety and efficacy of single-dose dupilumab in children with severe AD aged ≥6 months to <6 years.

METHODS

This open-label, multicenter, phase 2, sequential, two-age cohort, two-dose level study (LIBERTY AD PRE-SCHOOL; NCT03346434) included an initial cohort of older children aged ≥2 to <6 years, followed by a younger cohort aged ≥6 months to <2 years. Pharmacokinetic sampling, safety monitoring and efficacy assessments were performed during the 4-week period after a single subcutaneous injection of dupilumab, in two sequential dosing groups (3 mg/kg, then 6 mg/kg). The use of standardized, low-to-medium potency topical corticosteroids was allowed.

RESULTS

Forty patients were enrolled (20/age cohort, 10/dose level within a cohort) between December 20, 2017 and July 22, 2019. Within each age cohort, pharmacokinetic exposures after a single injection of dupilumab increased in a greater than dose-proportional manner. At week 3, treatment with 3 and 6 mg/kg dupilumab reduced scores of mean Eczema Area and Severity Index by -44.6% and -49.7% (older cohort) and -42.7% and -38.8% (younger cohort), and mean Peak Pruritus NRS scores by -22.9% and -44.7% (older cohort) and -11.1% and -18.2% (younger cohort), respectively. At week 4, improvements in most efficacy outcomes diminished in both age groups, particularly with the lower dose. The safety profile was comparable to that seen in adults, adolescents and children.

CONCLUSIONS

Single-dose dupilumab was generally well tolerated and substantially reduced clinical signs/symptoms of AD. Slightly better responses were seen in older than younger children. The pharmacokinetics of dupilumab were non-linear, consistent with previous studies in adults and adolescents.

Drug-Drug Interactions of Glecaprevir and Pibrentasvir Coadministered With Human Immunodeficiency Virus Antiretrovirals

BACKGROUND

Treatment of patients coinfected with hepatitis C and human immunodeficiency viruses (HCV; HIV) requires careful consideration of potential drug-drug interactions between HCV direct-acting antiviral agents (DAA) and HIV antiretrovirals. Glecaprevir/pibrentasvir is a fixed-dose combination of an NS3/4A protease inhibitor and an NS5A inhibitor approved for the treatment of chronic HCV genotype 1-6 infection, including patients with HIV coinfection.

METHODS

A series of phase 1 studies was conducted to evaluate potential interactions of glecaprevir and pibrentasvir with elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide, abacavir/dolutegravir/lamivudine, raltegravir, rilpivirine, atazanavir/ritonavir, darunavir/ritonavir, lopinavir/ritonavir, or efavirenz/emtricitabine/tenofovir disoproxil fumarate. Pharmacokinetics of the antiretrovirals and DAAs were characterized when administered alone and in combination to quantify changes in systemic drug exposure.

RESULTS

Glecaprevir area under the curve increased >4-fold in the presence of ritonavir-boosted HIV protease inhibitors, while pibrentasvir concentrations were not significantly affected; elevations in alanine transaminase occurred in combination with atazanavir/ritonavir only. Exposures of glecaprevir and pibrentasvir may be significantly decreased by efavirenz. Coadministration with glecaprevir and pibrentasvir did not result in clinically significant changes in the exposure of any antiretroviral agents.

CONCLUSIONS

Atazanavir is contraindicated with glecaprevir/pibrentasvir and use of boosted protease inhibitors or efavirenz is not recommended. No clinically significant interactions were observed with other studied antiretrovirals.

Dupilumab provides favourable long-term safety and efficacy in children aged ≥ 6 to < 12 years with uncontrolled severe atopic dermatitis: results from an open-label phase IIa study and subsequent phase III open-label extension study

Background

Children aged ≥ 6 to < 12 years with severe atopic dermatitis (AD) have limited treatment options. In a 16‐week, randomized, placebo‐controlled, phase III trial in children, dupilumab, a monoclonal antibody inhibiting interleukin (IL)‐4/IL‐13 signalling, significantly improved signs and symptoms with acceptable safety; longer‐term safety and efficacy data are lacking.

Objectives

To report the pharmacokinetic profile and long‐term safety and efficacy of dupilumab in children (aged ≥ 6 to < 12 years) with severe AD.

Methods

Children (aged ≥ 6 to < 12 years) with severe AD were enrolled in a global, multicentre, phase IIa, open‐label, ascending‐dose, sequential cohort study and subsequent open‐label extension (OLE) study. Patients received single‐dose dupilumab 2 or 4 mg kg⁻¹ followed by 8‐week pharmacokinetic sampling, then 2 or 4 mg kg⁻¹ weekly for 4 weeks (phase IIa), followed by the same weekly regimen (OLE). Primary endpoints were dupilumab concentration–time profile and treatment‐emergent adverse events (TEAEs); secondary assessments included Eczema Area and Severity Index (EASI) and Peak Pruritus Numeric Rating Scale (PP‐NRS) score.

Results

Of 38 children enrolled, 37 completed phase IIa and 33 continued to the OLE. Nonlinear, target‐mediated pharmacokinetics characterized dupilumab concentrations (week 24–48 mean serum concentrations: 2 mg kg⁻¹, 61–77 mg L⁻¹; 4 mg kg⁻¹, 143–181 mg L⁻¹). TEAEs were mostly mild to moderate and transient; none led to treatment discontinuation. The most commonly reported TEAEs were nasopharyngitis (2 mg kg⁻¹, 47%; 4 mg kg⁻¹, 56%) and AD exacerbation (29% and 13%, respectively). Single‐dose dupilumab rapidly improved AD with further improvements through week 52. Mean EASI and PP‐NRS improved by −37%/−33% and −17%/−20% at week 2 (phase IIa) and −92%/−84% and −70%/−58% at week 52 (OLE), respectively.

Conclusions

These safety and efficacy results support the use of dupilumab as a continuous long‐term treatment for children aged ≥ 6 to < 12 years with severe AD.

What is already known about this topic?

Severe atopic dermatitis (AD) has a marked negative impact on patient quality of life and can cause financial burden owing to a lack of effective treatments.

Dupilumab significantly improved signs and symptoms of AD with an acceptable safety profile in a 16‐week randomized, double‐blind, placebo‐controlled phase III study in children aged ≥ 6 to < 12 years with severe AD.

What does this study add?

This study extends information on the safety, efficacy and pharmacokinetic profile of dupilumab treatment for up to 52 weeks in children aged ≥ 6 to < 12 years with severe AD.

The results support the use of dupilumab as a continuous long‐term treatment for children aged ≥ 6 to < 12 years with severe AD.

Linked Comment: Sibbald. Br J Dermatol 2021; 184:792–793.

Drug-Drug Interactions of Tacrolimus or Cyclosporine With Glecaprevir and Pibrentasvir in Healthy Subjects

A fixed-dose combination of glecaprevir and pibrentasvir is approved for treatment of chronic infection with hepatitis C virus (HCV) genotypes 1-6. Three phase 1 open-label studies were conducted in healthy volunteers to evaluate the potential for clinically relevant drug-drug interactions of the glecaprevir 300-mg and pibrentasvir 120-mg combination with the immunosuppressants tacrolimus (1 mg) or cyclosporine (100 and 400 mg). Glecaprevir and pibrentasvir exposure was unaffected by tacrolimus, whereas the tacrolimus area under the curve (AUC) value was 45% higher with glecaprevir and pibrentasvir. Cyclosporine 100 mg had a limited effect on glecaprevir or pibrentasvir exposure (≤37% AUC increase), but cyclosporine 400 mg increased exposure of both glecaprevir and pibrentasvir (410% and 93% AUC increase, respectively). Cyclosporine concentration was unaffected by glecaprevir and pibrentasvir at either cyclosporine dose (≤14% AUC change). Adverse events were all grade 1 (mild), with the most common nausea and flushing attributed to cyclosporine. Findings from these studies supported evaluation of glecaprevir/pibrentasvir in HCV-infected kidney and liver transplant recipients receiving tacrolimus without additional dose adjustment or receiving cyclosporine up to 100 mg per day.

Efficacy and Pharmacokinetics of Glecaprevir and Pibrentasvir With Concurrent Use of Acid-Reducing Agents in Patients With Chronic HCV Infection

BACKGROUND & AIMS

Proton pump inhibitors (PPIs) are commonly prescribed to treat acid-related disorders. Some direct-acting antiviral regimens for chronic hepatitis C virus (HCV) infection have reduced efficacy in patients taking concomitant acid-reducing agents, including PPIs, due to interactions between drugs. We analyzed data from 9 multicenter, phase 2 and 3 trials to determine the efficacy and pharmacokinetics of an HCV therapeutic regimen comprising glecaprevir and pibrentasvir (glecaprevir/pibrentasvir) in patients taking concomitant acid-reducing agents.

METHODS

We analyzed data from 2369 patients infected with HCV genotypes 1-6 and compensated liver disease treated with an all-oral regimen of glecaprevir/pibrentasvir for 8-16 weeks. We compared efficacy and pharmacokinetics among patients receiving at least 1 dose of an acid-reducing agent (a PPI, an H2 blocker, or antacid). High-dose PPI was defined as daily dose greater than 20 mg omeprazole dose equivalent. The objectives were to evaluate rate of sustained virologic response 12 weeks post-treatment (SVR12) and to assess steady-state glecaprevir and pibrentasvir exposures in patients on acid-reducing agents.

RESULTS

Of the 401 patients (17%) who reported use of acid-reducing agents, 263 took PPIs (11%; 109 patients took a high-dose PPI and 154 patients took a low-dose PPI). Rates of SVR12 were 97.0% among patients who used acid-reducing agents and 97.5% among those not using acid-reducing agents (P = .6). An SVR12 was achieved in 96.3% taking a high-dose PPI and 97.4% taking a low-dose PPI, with no virologic failures in those receiving a high-dose PPI (P = .7). Glecaprevir, but not pibrentasvir, bioavailability was affected; its exposure decreased by 41% in patients taking a high-dose PPI.

CONCLUSIONS

In an analysis of data from 9 clinical trials, we observed a high rate of SVR12 (approximately 97%) among patients treated with glecaprevir/pibrentasvir for HCV infection-even among patients taking concomitant ARA or high-dose PPI. This was despite decreased glecaprevir exposures in patients when on high-dose PPIs. ClinicalTrials.gov numbers, NCT02243280 (SURVEYOR-I), NCT02243293 (SURVEYOR-II), NCT02604017 (ENDURANCE-1), NCT02640482 (ENDURANCE-2), NCT02640157 (ENDURANCE-3), NCT02636595 (ENDURANCE-4), NCT02642432 (EXPEDITION-1), NCT02651194 (EXPEDITION-4), NCT02446717 (MAGELLAN-I).

Efficacy and Safety of Glecaprevir/Pibrentasvir in Patients Coinfected With Hepatitis C Virus and Human Immunodeficiency Virus Type 1: The EXPEDITION-2 Study

Background

Once-daily glecaprevir coformulated with pibrentasvir (glecaprevir/pibrentasvir) demonstrated high rates of sustained virologic response 12 weeks after treatment (SVR12) in patients with hepatitis C virus (HCV) genotype 1-6 infection. This phase 3 study evaluated the efficacy and safety of glecaprevir/pibrentasvir in patients with chronic HCV genotype 1-6 and human immunodeficiency virus type 1 (HIV-1) coinfection, including patients with compensated cirrhosis.

Methods

EXPEDITION-2 was a phase 3, multicenter, open-label study evaluating glecaprevir/pibrentasvir (300 mg/120 mg) in HCV genotype 1-6/HIV-1-coinfected adults without and with compensated cirrhosis for 8 and 12 weeks, respectively. Patients were either HCV treatment-naive or experienced with sofosbuvir, ribavirin, or interferon, and antiretroviral therapy (ART) naive or on a stable ART regimen. Treatment-experienced genotype 3-infected patients were excluded. The primary endpoint was the SVR12 rate.

Results

In total, 153 patients were enrolled, including 16 (10%) with cirrhosis. The SVR12 rate was 98% (n = 150/153; 95% confidence interval, 95.8-100), with no virologic failures in 137 patients treated for 8 weeks. One genotype 3-infected patient with cirrhosis had on-treatment virologic failure. Most adverse events were mild in severity; 4 patients (2.6%) had serious adverse events, all deemed unrelated to glecaprevir/pibrentasvir. Treatment discontinuation was rare (<1%). All patients treated with ART maintained HIV-1 suppression (<200 copies/mL) during treatment.

Conclusions

Glecaprevir/pibrentasvir for 8 weeks in noncirrhotic and 12 weeks in cirrhotic patients is a highly efficacious and well-tolerated treatment for HCV/HIV-1 coinfection, regardless of baseline HCV load or prior treatment with interferon or sofosbuvir.

Clinical trial registration

NCT02738138.

Factor VIII associated with lipidic nanoparticles retains efficacy in the presence of anti-factor VIII antibodies in hemophilia A mice

The development of inhibitory antibodies against factor VIII (FVIII) is a major challenge in hemophilia A (HA) therapy. Such antibodies develop in nearly 30% of patients receiving replacement FVIII, abrogating therapeutic efficacy. This work evaluated whether B-domain deleted FVIII encapsulated in phosphatidylinositol containing lipid nanoparticles (PI-BDD FVIII) could serve as an efficacious FVIII replacement therapy in the presence of inhibitors. The HA mice were given clinically relevant doses of FVIII to develop inhibitors. The efficacy of free and PI-BDD FVIII was studied in inhibitor-positive HA mice using a tail clip assay. Mathematical modeling of these data was conducted to evaluate the hypothesis that lipid association sterically shields the protein from inhibitor binding. The immunization protocol resulted in a mean inhibitory titer level of 198 ± 52 BU/ml. Free BDD FVIII was ineffective at controlling blood loss in inhibitor-positive HA mice as early as 2 h post dose. In contrast, PI-BDD FVIII treated animals retained partial hemostatic efficacy as long as 18 h post dose. Mathematical modeling supports the hypotheses that a greater fraction of lipid-associated FVIII remains unbound to inhibitors and that PI-BDD FVIII has lower binding affinity to inhibitors than does the free protein. In addition, the modeling approaches extend current efforts to model the impact of immunogenicity on PK and the therapeutically meaningful endpoint of efficacy, thereby addressing an important knowledge gap, particularly in the FVIII scientific literature. Clinical translation of these findings could result in a significant improvement in the quality of care of inhibitor-positive HA patients. Copyright © 2016 John Wiley & Sons, Ltd.

Pharmacokinetics and Tolerability of a Dual Variable Domain Immunoglobulin ABT-981 Against IL-1α and IL-1β in Healthy Subjects and Patients With Osteoarthritis of the Knee

The interleukin (IL)-1 family of proinflammatory cytokines are thought to play a significant role in the structural progression of osteoarthritis and its associated symptoms. IL-1α and IL-1β are 2 distinct cytokines found in the cartilage, synovial membrane, and synovial fluid of patients with osteoarthritis. The aim of these studies was to evaluate the pharmacokinetics of ABT-981, a dual variable domain immunoglobulin (DVD-Ig) capable of simultaneously binding IL-1α and IL-1β, in healthy subjects and patients with osteoarthritis of the knee. Fifty-six healthy adult subjects were randomized to receive single doses of ABT-981 intravenously (0.3, 1, 3, or 10 mg/kg), subcutaneously (0.3, 1, 3 mg/kg), or matching placebo in a 3:1 ratio. Thirty-six patients with osteoarthritis of the knee were randomized to receive 4 subcutaneous ABT-981 doses of 0.3, 1, or 3 mg/kg administered every 2 weeks, 3 subcutaneous doses of ABT-981 3 mg/kg every 4 weeks, or matching placebo in a 7:2 active:placebo ratio. ABT-981 behaved similarly to conventional monoclonal antibodies following single or multiple doses with mean maximum serum concentrations 2 to 9 days after subcutaneous doses, mean terminal half-lives of 10 to 14 days, and an absolute subcutaneous bioavailability of 46%. Exposure of ABT-981 was approximately linear following single or multiple doses every 2 weeks with monoexponential decline of terminal-phase concentrations. The most common adverse events associated with ABT-981 were diarrhea and headache in healthy subjects and injection site erythema in subjects with osteoarthritis of the knee. Decreased absolute neutrophil counts were observed in response to ABT-981 administration.

Soy phosphatidylinositol containing nanoparticle prolongs hemostatic activity of B-domain deleted factor VIII in hemophilia A mice

Factor VIII (FVIII) replacement therapy in hemophilia A (HA) is complicated by a short half-life and high incidence of inhibitory antibody response against the protein. Phosphatidylinositol (PI) containing lipidic nanoparticles have previously been shown to reduce the immunogenicity and prolong the half-life of full length FVIII. It has not been established whether this prolongation in half-life improves hemostatic efficacy and whether this approach could be extended to the B-domain deleted form of FVIII (BDD FVIII). In the current study, we evaluated the pharmacokinetics (PK), hemostatic efficacy, and immunogenicity of BDD FVIII associated with PI nanoparticles (PI-BDD FVIII) in HA mice. Comparative human PK was predicted using an "informed scaling" approach. PI-BDD FVIII showed an approximate 1.5-fold increase in terminal half-life compared with free BDD FVIII following i.v. bolus doses of 40 IU/kg. PI-BDD FVIII-treated animals retained hemostatic efficacy longer than the free FVIII-treated group in a tail vein transection model of hemostasis. PI association reduced the development of inhibitory and binding antibodies against BDD FVIII after a series of i.v. injections. The combined improvements in circulating half-life and hemostatic efficacy could significantly prolong the time above clinically established therapeutic thresholds of prophylactic FVIII replacement therapy in humans.

Effects of replacement of factor VIII amino acids Asp519 and Glu665 with Val on plasma survival and efficacy in vivo

Proteolytic cleavage of factor VIII (FVIII) to activated FVIIIa is required for participation in the coagulation cascade. The A2 domain is no longer covalently bound in the resulting activated heterotrimer and is highly unstable. Aspartic acid (D) 519 and glutamic acid (E) 665 at the A1-A2 and A2-A3 domain interfaces were identified as acidic residues in local hydrophobic pockets. Replacement with hydrophobic valine (V; D519V/E665V) improved the stability and activity of the mutant FVIII over the wild-type (WT) protein in several in vitro assays. In the current study, we examined the impact of mutations on secondary and tertiary structure as well as in vivo stability, pharmacokinetics (PK), efficacy, and immunogenicity in a murine model of Hemophilia A (HA). Biophysical characterization was performed with far-UV circular dichroism (CD) and fluorescence emission studies. PK and efficacy of FVIII was studied following i.v. bolus doses of 4, 10 and 40 IU/kg with chromogenic and tail clip assays. Immunogenicity was measured with the Bethesda assay and ELISA after a series of i.v. injections. Native secondary and tertiary structure was unaltered between variants. PK profiles were similar at higher doses, but at 4 IU/kg plasma survival of D519V/E665V was improved. Hemostasis at low concentrations was improved for the mutant. Immune response was similar between variants. Overall, these results demonstrate that stabilizing mutations in the A2 domain of FVIII can improve HA therapy in vivo.

Nonlinear pharmacokinetics of factor VIII and its phosphatidylinositol lipidic complex in hemophilia A mice

Factor VIII (FVIII) is an important cofactor in the blood coagulation cascade and its deficiency or dysfunction causes hemophilia A (HA), a bleeding disorder. Replacement with recombinant FVIII is limited by a short half-life and the development of inhibitory antibodies. A phosphatidylinositol (PI) containing lipid nanoparticle was developed that, when associated with FVIII, reduces immunogenicity and prolongs circulation of the therapeutic protein in HA mice. A multiple dose level pharmacokinetic (PK) study of human free FVIII and its FVIII-PI complex over a clinically relevant range of doses (20, 40 and 200 IU/kg) was conducted in HA mice to investigate linearity of the PK and to determine if the reduced catabolism of FVIII following association with PI particles, previously only observed in the terminal phase following 400 IU/kg, could be extendable over a range of doses. The findings suggest that the disposition of FVIII is best characterized by a two-compartment model with saturable Michaelis-Menten elimination. Spontaneous complexation of FVIII with PI particles significantly increases plasma survival of the protein at 20 and 40 IU/kg doses. Human simulations at 40 IU/kg project an increase in the terminal half-life and the time to reach a minimum therapeutic threshold of 0.01 IU/ml of 5.4 h and 40 h, respectively, compared with free FVIII. Formulation with PI containing lipid particles may represent a viable delivery strategy for improving FVIII therapy.

Allometry of factor VIII and informed scaling of next-generation therapeutic proteins

Allometric scaling has been applied to the pharmacokinetics (PK) of factor VIII (FVIII), but published relationships are based on relatively small subsets of available data. Numerous next-generation forms of FVIII are being developed (e.g., Fc fusion, PEGylated, and liposomal formulations) and traditional PK scaling of these products would not incorporate the wealth of existing knowledge for current FVIII therapy in humans. We conducted a meta-analysis and developed allometric relationships of FVIII from over 100 PK studies collected from literature. Normalized Wajima curves were used to relate mean FVIII profiles between species. An "informed scaling" approach was derived for predicting first-in-human PK parameters and demonstrated with a case study for an Fc fusion FVIII. NCA values for FVIII PK were well described by the allometric equations CL = 6.59 W(0.85) and V(ss) = 65.0 W(0.97). A subset of studies characterized by two-compartment modeling showed strong linearity in scaling of total clearance (CL) and central volume, but more variability in distributional CL and peripheral volume. Wajima curves for FVIII superimposed across species and the disposition of Fc fusion FVIII in humans was well predicted by "informed scaling." This approach might be generally applicable for predicting human PK of next-generational therapeutics.

Native-like aggregates of factor VIII are immunogenic in von Willebrand factor deficient and hemophilia a mice

The administration of recombinant factor VIII (FVIII) is the first-line therapy for hemophilia A (HA), but 25%-35% of patients develop an inhibitory antibody response. In general, the presence of aggregates contributes to unwanted immunogenic responses against therapeutic proteins. FVIII has been shown to form both native-like and nonnative aggregates. Previously, we showed that nonnative aggregates of FVIII are less immunogenic than the native protein. Here, we investigated the effect of native-like aggregates of FVIII on immunogenicity in HA and von Willebrand factor knockout (vWF(-/-)) mice. Mice immunized with native-like aggregates showed significantly higher inhibitory antibody titers than animals that received native FVIII. Following restimulation in vitro with native FVIII, the activation of CD4+ T-cells isolated from mice immunized with native-like aggregates is approximately fourfold higher than mice immunized with the native protein. Furthermore, this is associated with increases in the secretion of proinflammatory cytokines IL-6 and IL-17 in the native-like aggregate treatment group. The results indicate that the native-like aggregates of FVIII are more immunogenic than native FVIII for both the B-cell and the T-cell responses.

PEGylation of a factor VIII-phosphatidylinositol complex: pharmacokinetics and immunogenicity in hemophilia A mice

Hemophilia A is an X-linked bleeding disorder caused by the deficiency of factor VIII (FVIII). Exogenous FVIII is administered therapeutically, and due to a short half-life, frequent infusions are often required. Fifteen to thirty-five percent of severe hemophilia A patients develop inhibitory antibodies toward FVIII that complicate clinical management of the disease. Previously, we used phosphatidylinositol (PI) containing lipidic nanoparticles to improve the therapeutic efficacy of recombinant FVIII by reducing immunogenicity and prolonging the circulating half-life. The objective of this study is to investigate further improvements in the FVIII-PI formulation resulting from the addition of polyethylene glycol (PEG) to the particle. PEGylation was achieved by passive transfer of PEG conjugated lipid into the FVIII-PI complex. PEGylated FVIII-PI (FVIII-PI/PEG) was generated with high association efficiency. Reduced activity in vitro and improved retention of activity in the presence of antibodies suggested strong shielding of FVIII by the particle; thus, in vivo studies were conducted in hemophilia A mice. Following intravenous administration, the apparent terminal half-life was improved versus both free FVIII and FVIII-PI, but exposure determined by area under the curve was reduced. The formation of inhibitory antibodies after subcutaneous immunization with FVIII-PI/PEG was lower than free FVIII but resulted in a significant increase in inhibitors following intravenous administration. Passive transfer of PEG onto the FVIII-PI complex does not provide any therapeutic benefit.

Immunogenicity and pharmacokinetic studies of recombinant factor VIII containing lipid cochleates

Replacement therapy using recombinant factor VIII (rFVIII) is currently the most common therapy for hemophilia A, a bleeding disorder caused by the deficiency of FVIII. However, 15-30% of patients develop inhibitory antibodies against administered rFVIII, which complicates the therapy. Encapsulation or association of protein with lipidic structures can reduce this immune response. Previous studies developed and characterized rFVIII-containing phosphatidylserine (PS) cochleate cylinders using biophysical techniques. It was hypothesized that these structures may provide a reduction in immunogenicity while avoiding the rapid clearance by the reticuloendothelial system (RES) previously observed with liposomal vesicles of similar composition. This study investigated in vivo behavior of the cochleates containing rFVIII including immunogenicity and pharmacokinetics in hemophilia A mice. The rFVIII-cochleate complex significantly reduced the level of inhibitory antibody developed against rFVIII following intravenous (i.v.) administration. Pharmacokinetic modeling allowed assessment of in vivo release kinetics. Cochleates acted as a delayed release delivery vehicle with an input peak of cochleates showed limited RES uptake and associated rFVIII displayed a similar disposition to the free protein upon release from the structure. Incomplete disassociation from the complex limits systemic availability of the protein. Further formulation efforts are warranted to regulate the rate and extent of release of rFVIII from cochleate complexes.

Delivery of therapeutic proteins

The safety and efficacy of protein therapeutics are limited by three interrelated pharmaceutical issues, in vitro and in vivo instability, immunogenicity and shorter half-lives. Novel drug modifications for overcoming these issues are under investigation and include covalent attachment of poly(ethylene glycol) (PEG), polysialic acid, or glycolic acid, as well as developing new formulations containing nanoparticulate or colloidal systems (e.g., liposomes, polymeric microspheres, polymeric nanoparticles). Such strategies have the potential to develop as next generation protein therapeutics. This review includes a general discussion on these delivery approaches.

Use of a folding model and in situ spectroscopic techniques for rational formulation development and stability testing of monoclonal antibody therapeutics

Aggregation is a critical issue that hampers the development of monoclonal antibody therapeutics (Mabs). Traditionally, aggregation is considered a process in which native forms of proteins are transformed into an unstable highly associated form through an intermediate formation step. Here we describe the unfolding of an antiCD40 antibody using a folding model based on Lumry-Eyring nucleated polymerization (LENP) model. This model captures several experimental features of the thermal unfolding of this protein as studied by common in situ biophysical techniques such as circular dichroism, fluorescence spectroscopy, and turbidity measurements. According to this model, the unfolding and aggregation of the antiCD40 antibody is determined by several distinct steps that include conformational change(s) to generate aggregation prone states, reversible oligomer formation, nucleation and growth as well as their kinetics, and the formation of higher order assemblies/aggregates. Furthermore, the loss of monomer is controlled by both thermodynamic (equilibrium unfolding) and kinetic determinants of the unfolding process. This approach captures both of these rate-limiting steps. It can be concluded that this approach is sensitive to formulation conditions such as protein concentration, changes in buffer conditions, and temperature stress. The potential use of this approach in formulation development and stability testing of Mabs is discussed.

Effect of route of administration of human recombinant factor VIII on its immunogenicity in Hemophilia A mice

Factor VIII is a multi-domain glycoprotein and is an essential cofactor in the blood coagulation cascade. Its deficiency or dysfunction causes Hemophilia A, a bleeding disorder. Replacement using exogenous recombinant Factor VIII (FVIII) is the first line of therapy for Hemophilia A. Immunogenicity, the development of binding (total) and neutralizing (inhibitory) antibody against administered protein is a clinical complication of the therapy. There are several product related factors such as presence of aggregates, route and frequency of administration and glycosylation have been shown to contribute to immunogenicity. The effect of route of administration of FVIII on antibody development in Hemophilia A is not completely understood. Here we investigated the effect of route of administration (s.c. or i.v.) on immunogenicity in Hemophilia A mice. The total and inhibitory titers were determined using ELISA and modified Bethesda Assay respectively. The results indicated that s.c. is more immunogenic compared to i.v. route in terms of total antibody titer development (binding antibodies) but no significant differences in inhibitory titer levels could be established.

Role of glycosylation in conformational stability, activity, macromolecular interaction and immunogenicity of recombinant human factor VIII

Factor VIII (FVIII) is a multi-domain glycoprotein that is an essential cofactor in the blood coagulation cascade. Its deficiency or dysfunction causes hemophilia A, a bleeding disorder. Replacement using exogenous recombinant human factor VIII (rFVIII) is the first line of therapy for hemophilia A. The role of glycosylation on the activity, stability, protein-lipid interaction, and immunogenicity of FVIII is not known. In order to investigate the role of glycosylation, a deglycosylated form of FVIII was generated by enzymatic cleavage of carbohydrate chains. The biochemical properties of fully glycosylated and completely deglycosylated forms of rFVIII (degly rFVIII) were compared using enzyme-linked immunosorbent assay, size exclusion chromatography, and clotting activity studies. The biological activity of degly FVIII decreased in comparison to the fully glycosylated protein. The ability of degly rFVIII to interact with phosphatidylserine containing membranes was partly impaired. Data suggested that glycosylation significantly influences the stability and the biologically relevant macromolecular interactions of FVIII. The effect of glycosylation on immunogenicity was investigated in a murine model of hemophilia A. Studies showed that deletion of glycosylation did not increase immunogenicity.