Pharmacotherapeutic group: Immunosuppressants, selective immunosuppressants.
ATC code: L04AA36.
Pharmacology: Pharmacodynamics: Mechanism of action: Ocrelizumab is a recombinant humanised monoclonal antibody that selectively targets CD20-expressing B cells.
CD20 is a cell surface antigen found on pre-B cells, mature and memory B cells but not expressed on lymphoid stem cells and plasma cells.
The precise mechanisms through which ocrelizumab exerts its therapeutic clinical effects in MS is not fully elucidated but is presumed to involve immunomodulation through the reduction in the number and function of CD20-expressing B cells. Following cell surface binding, ocrelizumab selectively depletes CD20-expressing B cells through antibody-dependent cellular phagocytosis (ADCP), antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and apoptosis. The capacity of B-cell reconstitution and pre-existing humoral immunity are preserved. In addition, innate immunity and total T-cell numbers are not affected.
Pharmacodynamic effects: Treatment with ocrelizumab leads to rapid depletion of CD19+ B cells in blood by 14 days post treatment (first time-point of assessment) as an expected pharmacologic effect. This was sustained throughout the treatment period. For the B-cell counts, CD19 is used, as the presence of ocrelizumab interferes with the recognition of CD20 by the assay.
In the Phase III studies, between each dose of ocrelizumab, up to 5% of patients showed B-cell repletion (>lower limit of normal (LLN) or baseline) at least at one time point. The extent and duration of B-cell depletion was consistent in the PPMS and RMS trials.
The longest follow up time after the last infusion (Phase II study WA21493, N=51) indicates that the median time to B-cell repletion (return to baseline/LLN whichever occurred first) was 72 weeks (range 27-175 weeks). 90% of all patients had their B-cells repleted to LLN or baseline by approximately two and a half years after the last infusion.
Clinical efficacy and safety: Relapsing forms of multiple sclerosis (RMS): Efficacy and safety of ocrelizumab were evaluated in two randomised, double-blind, double-dummy, active comparator-controlled clinical trials (WA21092 and WA21093), with identical design, in patients with relapsing forms of MS (in accordance with McDonald criteria 2010) and evidence of disease activity (as defined by clinical or imaging features) within the previous two years. Study design and baseline characteristics of the study population are summarised in Table 1.
Demographic and baseline characteristics were well balanced across the two treatment groups. Patients receiving ocrelizumab (Group A) were given 600 mg every 6 months (Dose 1 as 2 x 300 mg intravenous infusions, administered 2 weeks apart, and subsequent doses were administered as a single 600 mg intravenous infusion). Patients in Group B were administered Interferon beta-1a 44 mcg via subcutaneous injection 3 times per week. (See Table 1.)
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Key clinical and MRI efficacy results are presented in Table 2 and Figure 1.
The results of these studies show that ocrelizumab significantly suppressed relapses, sub-clinical disease activity measured by MRI, and disease progression compared with interferon beta-1a 44 mcg subcutaneous. (See Table 2 and Figure 1.)
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Results of the pre-specified pooled analyses of time to CDP sustained for at least 12 weeks (40% risk reduction for ocrelizumab compared to interferon beta-1a (p=0.0006) were highly consistent with the results sustained for at least 24 weeks (40% risk reduction for ocrelizumab compared to interferon beta-1a, p=0.0025).
The studies enrolled patients with active disease. These included both active treatment naive and previously treated inadequate responders, as defined by clinical or imaging features. Analysis of patient populations with differing baseline levels of disease activity, including active and highly active disease, showed that the efficacy of ocrelizumab on ARR and 12 week CDP was consistent with the overall population.
Primary progressive multiple sclerosis (PPMS): Efficacy and safety of ocrelizumab were also evaluated in a randomised, double-blind, placebo-controlled clinical trial in patients with primary progressive MS (Study WA25046) who were early in their disease course according to the main inclusion criteria, i.e.: ages 18-55 years, inclusive; EDSS at screening from 3.0 to 6.5 points; disease duration from the onset of MS symptoms less than 10 years in patients with an EDSS at screening ≤5.0 or less than 15 years in patients with an EDSS at screening >5.0. With regard to disease activity, features characteristic of inflammatory activity, even in progressive MS, can be imaging-related, (i.e. T1 Gd-enhancing lesions and/or active [new or enlarging] T2 lesions). MRI evidence should be used to confirm inflammatory activity in all patients. Patients over 55 years of age were not studied. Study design and baseline characteristics of the study population are presented in Table 3.
Demographic and baseline characteristics were well balanced across the two treatment groups. Cranial MRI showed imaging features characteristic of inflammatory activity either by T1 Gd enhancing lesions or T2 lesions.
During the Phase 3 PPMS study, patients received 600 mg ocrelizumab every 6 months as two 300 mg infusions, given two weeks apart, throughout the treatment period. The 600 mg infusions in RMS and the 2 x 300 mg infusions in PPMS demonstrated consistent PK/PD profiles. IRR profiles per infusion were also similar, independent of whether the 600 mg dose was administered as a single 600 mg infusion or as two 300 mg infusions separated by two weeks (see Adverse Reactions and Pharmacology: Pharmacokinetics under Actions), but due to overall more infusions with the 2 x 300 mg regimen, the total number of IRRs were higher. Therefore, after Dose 1 it is recommended to administer ocrelizumab in a 600 mg single infusion (see Dosage & Administration) to reduce the total number of infusions (with concurrent exposure to prophylactic methylprednisolone and an antihistamine) and the related infusion reactions. (See Table 3.)
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Key clinical and MRI efficacy results are presented in Table 4 and Figure 2.
The results of this study show that ocrelizumab significantly delays disease progression and reduces deterioration in walking speed compared with placebo. (See Table 4 and Figure 2.)
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Pre-specified non-powered subgroup analysis of the primary endpoint suggests that patients who are younger or those with T1 Gd-enhancing lesions at baseline receive a greater treatment benefit than patients who are older or without T1 Gd-enhancing lesions (≤45 years: HR 0.64 [0.45, 0.92], >45 years: HR 0.88 [0.62, 1.26]; with T1 Gd-enhancing lesions at baseline: HR 0.65 [0.40-1.06], without T1 Gd-enhancing lesions at baseline: HR 0.84 [0.62-1.13]).
Moreover, post-hoc analyses suggested that younger patients with T1 Gd-enhancing lesions at baseline have the better treatment effect (≤45 years: HR 0.52 [0.27-1.00]; ≤46 years [median age of the WA25046 study]; HR 0.48 [0.25-0.92]; <51 years: HR 0.53 [0.31-0.89]).
Post-hoc analyses were performed in the Extended Controlled Period (ECP), which includes double-blinded treatment and approximately 9 additional months of controlled follow-up before continuing into the Open-Label Extension (OLE) or until withdrawal from study treatment. The proportion of patients with 24 week Confirmed Disability Progression of EDSS≥7.0 (24W-CDP of EDSS≥7.0, time to wheelchair) was 9.1% in the placebo group compared to 4.8% in the ocrelizumab group at Week 144, resulting in a 47% risk reduction of the time to wheelchair (HR 0.53, [0.31, 0.92]) during the ECP. As these results were exploratory in nature and included data after unblinding, the results should be interpreted with caution.
Shorter infusion substudy: The safety of the shorter (2-hour) ocrelizumab infusion was evaluated in a prospective, multicenter, randomised, double-blind, controlled, parallel arm substudy to Study MA30143 (Ensemble) in patients with Relapsing-Remitting Multiple Sclerosis that were naïve to other disease modifying treatments. The first dose was administered as two 300 mg infusions (600 mg total) separated by 14 days. Patients were randomised from their second dose onwards (Dose 2 to 6) in a 1:1 ratio to either the conventional infusion group with ocrelizumab infused over approximately 3.5 hours every 24 weeks, or the shorter infusion group with ocrelizumab infused over approximately 2 hours every 24 weeks. The randomisation was stratified by region and the dose at which patients were first randomised.
The primary endpoint was the proportion of patients with IRRs occurring during or within 24 hours following the first randomised infusion. The primary analysis was performed when 580 patients were randomised. The proportion of patients with IRRs occurring during or within 24 hours following the first randomised infusion was 24.6% in the shorter infusion compared to 23.1% in the conventional infusion group. The stratified group difference was similar. Overall, in all randomised doses, the majority of the IRRs were mild or moderate and only two IRRs were severe in intensity, with one severe IRR in each group. There were no life-threatening, fatal, or serious IRRs.
Immunogenicity: Patients in MS trials (WA21092, WA21093 and WA25046) were tested at multiple time points (baseline and every 6 months post treatment for the duration of the trial) for anti-drug antibodies (ADAs). Out of 1311 patients treated with ocrelizumab, 12 (~1%) tested positive for treatment-emergent ADAs, of which 2 patients tested positive for neutralising antibodies. The impact of treatment-emergent ADAs on safety and efficacy cannot be assessed given the low incidence of ADA associated with ocrelizumab.
Immunisations: In a randomised open-label study in RMS patients (N=102), the percentage of patients with a positive response to tetanus vaccine at 8 weeks after vaccination was 23.9% in the ocrelizumab group compared to 54.5% in the control group (no disease-modifying therapy except interferon-beta). Geometric mean anti-tetanus toxoid specific antibody titers at 8 weeks were 3.74 and 9.81 IU/ml, respectively. Positive response to ≥5 serotypes in 23-PPV at 4 weeks after vaccination was 71.6% in the ocrelizumab group and 100% in the control group. In patients treated with ocrelizumab a booster vaccine (13-PCV) given 4 weeks after 23-PPV did not markedly enhance the response to 12 serotypes in common with 23-PPV. The percentage of patients with seroprotective titers against five influenza strains ranged from 20.0-60.0% and 16.7-43.8% pre-vaccination and at 4 weeks post vaccination from 55.6-80.0% in patients treated with ocrelizumab and 75.0-97.0% in the control group, respectively. See Precautions and Interactions.
Pharmacokinetics: The pharmacokinetics of ocrelizumab in the MS studies were described by a two compartment model with time-dependent clearance, and with PK parameters typical for an IgG1 monoclonal antibody. The overall exposure (AUC over the 24 weeks dosing interval) was identical in the 2 x 300 mg in PPMS and 1 x 600 mg in RMS studies, as expected given an identical dose was administered. Area under the curve (AUCτ) after the 4th dose of 600 mg ocrelizumab was 3510 µg/mL•day, and mean maximum concentration (C
max) was 212 µg/mL in RMS (600 mg infusion) and 141 µg/mL in PPMS (300 mg infusions).
Absorption: Ocrelizumab is administered as an intravenous infusion. There have been no studies performed with other routes of administration.
Distribution: The population pharmacokinetics estimate of the central volume of distribution was 2.78 L. Peripheral volume and inter-compartment clearance were estimated at 2.68 L and 0.294 L/day.
Biotransformation: The metabolism of ocrelizumab has not been directly studied, as antibodies are cleared principally by catabolism (i.e. breakdown into peptides and amino acids).
Elimination: Constant clearance was estimated at 0.17 L/day, and initial time-dependent clearance at 0.0489 L/day which declined with a half-life of 33 weeks. The terminal elimination half-life of ocrelizumab was 26 days.
Special populations: Paediatric population: No studies have been conducted to investigate the pharmacokinetics of ocrelizumab in children and adolescents less than 18 years of age.
Elderly: There are no dedicated PK studies of ocrelizumab in patients ≥55 years due to limited clinical experience (see Dosage & Administration).
Renal impairment: No formal pharmacokinetic study has been conducted. Patients with mild renal impairment were included in clinical trials and no change in the pharmacokinetics of ocrelizumab was observed in those patients. There is no PK information available in patients with moderate or severe renal impairment.
Hepatic impairment: No formal pharmacokinetic study has been conducted. Patients with mild hepatic impairment were included in clinical trials, and no change in the pharmacokinetics was observed in those patients. There is no PK information available in patients with moderate or severe hepatic impairment.
Toxicology: Preclinical safety data: Non-clinical data reveal no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, and embryo-foetal development. Neither carcinogenicity nor mutagenicity studies have been conducted with ocrelizumab.
In two pre- and post-natal development studies in cynomolgus monkeys, administration of ocrelizumab from gestation day 20 to at least parturition was associated with glomerulopathy, lymphoid follicle formation in bone marrow, lymphoplasmacytic renal inflammation, and decreased testicular weight in offspring. The maternal doses administered in these studies resulted in maximum mean serum concentrations (C
max) that were 4.5- to 21-fold above those anticipated in the clinical setting.
There were five cases of neonatal moribundities, one attributed to weakness due to premature birth accompanied by opportunistic bacterial infection, one due to an infective meningoencephalitis involving the cerebellum of the neonate from a maternal dam with an active bacterial infection (mastitis) and three with evidence of jaundice and hepatic damage, with a viral aetiology suspected, possibly a polyomavirus. The course of these five confirmed or suspected infections could have potentially been impacted by B-cell depletion. Newborn offspring of maternal animals exposed to ocrelizumab were noted to have depleted B cell populations during the post-natal phase. Measurable levels of ocrelizumab were detected in milk (approximated 0.2% of steady state trough serum levels) during the lactation period.