Summary Basis of Decision for Tyruko

Tyruko was developed as a biosimilar of the reference biologic drug, Tysabri. The weight of evidence of similarity between a biosimilar and the reference biologic drug is provided by structural and functional studies. Biosimilars are manufactured to the same regulatory standards as other biologic drugs. In addition to a typical chemistry and manufacturing data package that is submitted for a standard new biologic drug, biosimilar submissions include extensive data demonstrating similarity to the reference biologic drug.

Comparative Structural and Functional Studies

The biosimilarity evaluation was conducted as a three-way analytical assessment using Tyruko and the reference biologic product Tysabri authorized in the European Union (herein referred to as EU-Tysabri), as well as Tysabri authorized in the United States (herein referred to as US-Tysabri). Health Canada considers EU-Tysabri a suitable proxy for Tysabri authorized in Canada, as it meets all of the requirements for a non-Canadian reference biologic drug set forth in the Guidance Document: Information and Submission Requirements for Biosimilar Biologic Drugs. A bridging report of EU-Tysabri and US-Tysabri has been provided and showed similarity with regard to biological function and comparable degradation pathway and kinetics between both sourced products.

The biosimilarity assessment included the comparison of physicochemical, biophysical, and in vitro functional properties, as well as comparative stability and forced degradation studies under long-term, accelerated, and stress conditions. The results of the biosimilarity assessment demonstrated that Tyruko is similar to EU-Tysabri and US-Tysabri with regard to most of the quality attributes pertaining to physicochemical properties, higher-order structures, purity/impurity profiles, and biological activity. Comparative stability and forced degradation studies demonstrated similar stability and degradation profiles between Tyruko and the two reference drug products, with no new impurities detected. Some minor analytical differences in biochemical attributes were observed, however, these differences were not considered clinically meaningful as they had no impact on the biological activity of the drug. Overall, the comparative study results demonstrated that Tyruko is similar to both the EU-Tysabri and the US-Tysabri.

Characterization of the Drug Substance

Natalizumab is a recombinant humanized immunoglobulin G4κ monoclonal antibody that binds to the α4-subunit of human integrins. Its molecular weight is 149 kDa.

Detailed characterization studies were performed to provide assurance that natalizumab consistently exhibits the desired characteristic structure and biological activity.

Results from process validation studies indicate that the processing steps adequately control the levels of product- and process-related impurities. The impurities that were reported and characterized were found to be within established and acceptable limits. A risk assessment for the potential presence of nitrosamine impurities was conducted according to requirements outlined in Health Canada’s Guidance on Nitrosamine Impurities in Medications. The risks relating to the potential presence of nitrosamine impurities in the drug substance and/or drug product are considered negligible or have been adequately addressed (e.g., with qualified limits and a suitable control strategy).

Manufacturing Process of the Drug Substance and Drug Product and Process Controls

The drug substance is produced using a Chinese hamster ovary cell line that is genetically engineered to express the protein. The manufacture is based on a master and working cell bank system, where the master and working cell banks have been thoroughly characterized and tested for adventitious contaminants and endogenous viruses in accordance with International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) guidelines. Results from genetic characterization studies also demonstrated stability of these cell banks.

The manufacturing process of the drug substance involves inoculation of the contents of one vial of working cell bank into a sterile shake flask, cell propagation in additional shake flasks, inoculum expansion in bioreactors, then growth at a larger scale in a production bioreactor that uses a fed-batch process. Downstream purification involves three chromatography steps, viral inactivation, viral filtration, formulation, and further filtration. The drug substance is then filled into sterile bottles and stored at 2 °C to 8 °C.

The manufacturing process for the drug product involves drug substance pooling and mixing, bioburden and sterile filtration, and aseptic filling into glass vials. The drug product is stored at 2 °C to 8 °C, protected from light.

Tyruko drug product is a sterile, colourless, and clear to slightly opalescent concentrated solution, free of preservatives. Prior to intravenous infusion, the drug product is diluted in 100 mL of 0.9% sodium chloride injection solution. None of the non-medicinal ingredients (excipients) in the drug product are prohibited for use in drug products by the Food and Drug Regulations. The compatibility of the natalizumab with the excipients is supported by the stability data provided.

Process validation was conducted with four consecutive drug substance batches and three consecutive drug product batches manufactured at the intended scale. Process performance qualification data demonstrate that the manufacturing process is capable of consistently manufacturing the drug substance and drug product at the proposed batch-size ranges. All process parameters, in-process controls, release testing results, and stability results were consistent between batches and met predefined criteria, acceptance limits, and specifications. All ancillary validation studies were deemed successful and supportive of intermediate hold times, impurity clearance, resin lifetimes, filters, aseptic filling (media fills), extractables and leachables testing, shipping, and other supporting activities.

The materials used in the manufacture of the drug substance and drug product (including biological materials) are considered suitable and/or meet standards appropriate for their intended use. The manufacturing process is considered to be adequately controlled within justified limits

Control of the Drug Substance and Drug Product

The control strategy governing the manufacturing processes involves appropriately justified process parameters and in-process controls. Raw materials used in the manufacturing processes are of suitable quality and comply with in-house or compendial requirements. All excipients are commonly used in parenteral antibody formulations and comply with compendial requirements. No novel excipients were used. The proposed release and stability specifications for the drug substance and drug product are considered suitable to control for identity, protein content, purity/impurities, biological activity, and safety. Analytical testing is carried out using compendial and non-compendial methods that have been verified or validated to be fit for purpose and to adequately support the established specifications and the control strategy. A two-tiered reference standard program is in place to qualify current and future primary and working reference materials.

Tyruko is a Schedule D (biologic) drug and is, therefore, subject to Health Canada's Lot Release Program as per the Guidance for Sponsors: Lot Release Program for Schedule D (Biologic) Drugs.

Stability of the Drug Substance and Drug Product

Based on the stability data submitted, the proposed shelf life and storage conditions for the drug substance and drug product were adequately supported and are considered to be satisfactory. The proposed 36-month shelf life at 2 °C to 8 °C for Tyruko is considered acceptable when protected from light. The in-use storage time after dilution in saline is no more than 24 hours when stored at 2 °C to 8 °C.

The compatibility of the drug product with the container closure system was demonstrated through compendial testing and stability studies. The container closure system met all validation test acceptance criteria.

The proposed packaging and components are considered acceptable.

Facilities and Equipment

The design, operations, and controls of all facilities and equipment involved in the production are considered suitable.

On-site evaluations (OSEs) of the facilities involved in the manufacture and testing of the drug substance and drug product were not conducted as the review of the quality component of the New Drug Submission for Tyruko was based primarily on the foreign review.

All sites involved in production are compliant with good manufacturing practices.

Adventitious Agents Safety Evaluation

The natalizumab manufacturing process incorporates adequate control measures to prevent contamination and maintain microbial control. Pre-harvest culture fluid from each lot is tested to ensure absence of adventitious microorganisms (bioburden, mycoplasma, and viruses) and appropriate limits are set. Purification process steps designed to remove and inactivate viruses are adequately validated.

The drug substance manufacturing process was appropriately validated to support the robust clearance and inactivation of adventitious agents as per ICH Q5A (R2). The calculated minimum retroviral safety factor is 11.8 log, or 1 retrovirus-like particle per 2.16 x 10⁶ doses, which is consistent with the safety margin for CHO-derived recombinant proteins in ICH Q5A (R2).

Materials of biological origin are properly sourced and tested. The biologic raw materials originate from sources with no or minimal risk of transmissible spongiform encephalopathy agents or other human pathogens. A certification letter attesting to these claims was provided by the sponsor. The excipients used in the drug product formulation are not of animal or human origin.

For biosimilars, the degree of similarity to the reference biologic drug at the quality level determines the scope and the breadth of the required non-clinical data. Non-clinical studies serve to complement the structural and functional studies and address potential areas of residual uncertainty. The non-clinical database submitted for Tyruko was in compliance with the requirements for non-clinical studies of biosimilars, as presented in the Guidance Document: Information and Submission Requirements for Biosimilar Biologic Drugs.

Data from six method validation studies and one 4-week repeat-dose toxicity study were included in the submission. The results of the validation studies confirmed that the methods employed were suitable for detection and quantification of natalizumab molecules. The repeat-dose toxicity study compared the potential toxicity of Tyruko and the reference product, EU-Tysabri, following intravenous administration to treatment-naïve cynomolgus monkeys over a period of 4 weeks. There were no noteworthy differences in the toxicity profiles between Tyruko and EU-Tysabri. Both products were well tolerated and all study observations were consistent with the known pharmacodynamic effects of natalizumab. The observations reported in the toxicity study are consistent with previous observations for Tysabri.

In view of the intended use of Tyruko, there are no pharmacological or toxicological issues within this submission which preclude authorization of the product.

The purpose of the clinical program for a biosimilar is to demonstrate that there are no clinically meaningful differences between the biosimilar and the reference biologic drug. The structural complexity of the biologic drug and availability of a relevant and sensitive pharmacodynamic endpoint determine the scope and the breadth of the required clinical data. The clinical program is designed to complement the structural and functional studies and address potential areas of residual uncertainty.

Comparative Pharmacokinetics, Pharmacodynamics, and Immunogenicity

Multiple sclerosis is an autoimmune demyelinating and neurodegenerative disease of the central nervous system.

Natalizumab, the medicinal ingredient in Tyruko, is a selective adhesion molecule inhibitor that binds to the α4 subunit of human integrin, which is highly expressed on the surface of all leukocytes, excluding neutrophils. By binding to the α4β1 and α4β7 integrins, natalizumab blocks their interactions with their cognate receptors, vascular cell adhesion molecule-1 (VCAM-1) and mucosal vascular addressin cell adhesion molecule-1 (MadCAM-1), respectively. This blockade prevents the transmigration of mononuclear leukocytes (including T-lymphocytes) across the endothelium into inflamed parenchymal tissue, including across the blood-brain barrier. This action may reduce inflammatory activity present in the brain of patients with multiple sclerosis and inhibit further recruitment of immune cells into inflamed tissue, thus reducing the formation or enlargement of multiple sclerosis lesions.

Clinical pharmacology data in support of Tyruko were provided from the main Phase I comparative bioavailability study (PB006-01-03) performed in healthy subjects, as well as from a supportive comparative Phase I pilot study (PB006-01-01).

Study PB006-01-03 was a single dose, randomized, double-blind, parallel-group study that compared the pharmacokinetics and pharmacodynamics of Tyruko, Tysabri authorized in the European Union (herein referred to as EU-Tysabri), and Tysabri authorized in the United States (herein referred to as US-Tysabri) in healthy subjects.

The sponsor designated EU-Tysabri as the reference biologic drug throughout this New Drug Submission. As such, the review focused on the comparative data between Tyruko and EU-Tysabri, whereas the US-Tysabri data were used as supportive, where appropriate. Consistent pharmacokinetic and immunogenicity data were observed between EU- and US-Tysabri in this study.

The primary objective of Study PB006-01-03 was to demonstrate pharmacokinetic comparability of Tyruko to EU-Tysabri, and to US-Tysabri in healthy adult subjects, as assessed by the area under the concentration-time curve (AUC) from time zero extrapolated to infinity (AUC_inf) and the maximum observed serum concentration (C_max). The AUC to last measurable timepoint (AUC_T) was a secondary pharmacokinetic endpoint. Additional primary objectives included demonstrating the pharmacodynamic comparability of Tyruko to both EU-Tysabri and US-Tysabri in terms of the area under the effect curve from time zero to 12 weeks (AUEC_0-12w) for α4-integrin percent receptor saturation and the AUEC_0-12w for baseline-adjusted CD19+.

In total, 453 subjects were randomized in a 1:1:1 ratio to receive a single 3 mg/kg intravenous infusion of either Tyruko (149 subjects), EU-Tysabri (150 subjects) or US-Tysabri (150 subjects). Subject demographic characteristics and disposition were balanced across all three treatment arms. Review of the statistical analysis plan showed that the sample size provided greater than 90% statistical power to assess comparative bioavailability and was deemed appropriate.

Bioequivalence standards were met when comparing exposure of Tyruko and the reference drug (EU-Tysabri) and the supportive drug (US-Tysabri). Specifically, the point estimate and 90% confidence interval (CI) for AUC_0-t between Tyruko and EU-Tysabri was 0.9864 [CI: 0.9387, 1.0316]. The point estimates for C_max between Tyruko and EU-Tysabri was 0.9565. Health Canada conducted an independent reanalysis of the pharmacokinetics data, taking into consideration the potency of Tyruko and EU-Tysabri. From this analysis, both the potency-corrected and the uncorrected point estimates for both the C_max and the 90% CI bounds of AUC_T between Tyruko and EU-Tysabri were contained within Health Canada’s comparative bioavailability standards of 0.80 to 1.25. The uncorrected values presented in the study are consistent with Health Canada’s analysis.

In support of the pharmacokinetic data, there were consistent responses amongst subjects in all three arms when analyzing two primary pharmacodynamic endpoints (CD19+ levels and α4-integrin percent receptor saturation). Both the AUEC_0-12w for α4-integrin percent receptor saturation and the AUEC_0-12w for baseline-adjusted CD19+ had 90% CIs within the Health Canada recommended margin of 80.0% to 125.0% for Tyruko versus EU-Tysabri.

Treatment with any therapeutic protein is accompanied by the risk of immunogenicity (the development of anti-drug antibodies [ADAs], which have the potential to neutralize the biological activity of the drug). The immunogenicity profiles were consistent for all three treatment arms of Study PB006-01-3, suggesting that there is little immunogenic difference between the drugs when administered to a healthy population. Across all three groups, approximately equal proportions of subjects had detectable anti-drug antibodies and neutralizing antibodies to natalizumab.

Together, the pharmacokinetic and pharmacodynamic statistical results support the conclusion of biosimilarity of Tyruko and EU-Tysabri. Supportive evidence from the US-Tysabri datasets further strengthened the conclusions of biosimilarity. There were no clinically meaningful differences in immunogenicity between Tyruko and EU-Tysabri.

Comparative Clinical Efficacy and Safety

The comparative clinical efficacy of Tyruko and its reference biologic drug, EU-Tysabri, was primarily evaluated in the confirmatory, Phase III, multicentre, double-blind, active-controlled, randomized, parallel-group Study PB006-03-01 conducted in adult patients with relapsing-remitting multiple sclerosis (RRMS). The aim of the study was to demonstrate no clinically meaningful differences between Tyruko and EU-Tysabri in terms of efficacy, safety, and immunogenicity. The primary objective of the study was to evaluate and compare the cumulative number of new active lesions (assessed by magnetic resonance imaging) over 24 weeks.

A total of 264 patients with RRMS were randomized 1:1 and received treatment with Tyruko (132 patients) or EU-Tysabri (133 patients) as intravenous infusions every 4 weeks, starting at Visit 1 (Week 0) through Visit 12 (Week 44), for a total of 12 infusions. All patients were White. The majority of patients were female (59 to 64% across groups), with a mean age of 37 years, and mean weight of approximately 70 kg.

The primary efficacy endpoint was the cumulative number of new active lesions over 24 weeks. The point estimate (standard error [SE]) for the exponentiated difference in the cumulative number of new lesions between EU-Tysabri and the Tyruko group was 0.17 (0.397), with a 95% CI of -0.613 to 0.944, which falls within the acceptable predefined margin of -2.1 to 2.1.

The results of the secondary efficacy endpoints of annualized relapse rate and Expanded Disability Status Scale (EDSS) score were supportive in showing a consistent treatment benefit between EU-Tysabri and Tyruko.

Overall, the percentages of patients with treatment-emergent adverse events (TEAEs) and with TEAEs related to study drug were similar across groups. Approximately two-thirds of patients in each group reported at least one TEAE, while approximately 25% of patients in each group reported a study drug-related TEAE. Few patients experienced TEAEs that were Grade 3 in severity, adverse events of special interest, serious adverse events, or adverse events leading to study drug discontinuation or withdrawal. The incidence of Grade 3 TEAEs and of TEAEs leading to discontinuation were higher in the Tyruko group than in the other groups, although, this difference was not considered clinically meaningful. No fatal TEAEs were reported in the study.

During review of the New Drug Submission, Health Canada became aware of concerns regarding a potential increased disability associated with delayed hypersensitivity in patients taking Tyruko. Health Canada will monitor this issue by requesting a Periodic Safety Update Report (PSUR)/Periodic Benefit-Risk Evaluation Report (PBRER) to assess the safety of Tyruko in the real-world, post-marketing clinical practice. The PBRER/PSUR should provide spontaneously reported data, as well as the outcomes of investigations ongoing in other jurisdictions. 

It is known that natalizumab therapy increases the risk of developing progressive multifocal leukoencephalopathy (PML), a rare but fatal central nervous system disease due to opportunistic infection caused by John Cunningham virus (JCV). Testing for the presence of anti-JCV antibodies is recommended as a risk mitigation measure prior to and during natalizumab therapy. This recommendation is described in the Product Monograph for the reference drug Tysabri, which refers to the use of a Health Canada-licensed anti-JCV antibodies assay to test patients considering or receiving natalizumab therapy. This assay, however, is not accessible to patients treated with a biosimilar product, such as Tyruko.

The sponsor has developed their own anti-JCV antibodies assay for use with Tyruko, but it will not be commercialized in Canada. Instead, they propose to ship patients’ samples for testing in Europe, where the assay has been authorized. The sponsor provided data to demonstrate the comparability of both assays. Following a high-level review, Health Canada concluded that the assays are sufficiently comparable and that the assay proposed for Tyruko demonstrated satisfactory analytical validity. Health Canada has advised the sponsor that after Tyruko enters the Canadian market, the sample collection sets sent to healthcare professionals in Canada must be prepared in compliance with relevant Canadian regulatory requirements. The Product Monograph for Tyruko provides clear guidance and instructions for healthcare professionals on initiating patient testing prior to commencing treatment with Tyruko.

As with Tysabri, the major identified safety concern associated with the use of Tyruko is an increased risk of PML and/or granule cell neuronopathy (GCN) secondary to opportunistic infection caused by John Cunningham virus (JCV). Both PML and JCV-GCN can cause disability or death. Therefore, a Serious Warnings and Precautions box highlighting this risk has been included in the Product Monograph for Tyruko, as is found in the Product Monograph for Tysabri. The box cautions healthcare professionals to monitor patients taking Tyruko for any new sign or symptom that may be suggestive of PML and/or JCV-GCN. Moreover, it emphasizes that Tyruko dosing should be withheld immediately at the first sign or symptom that may be suggestive of either PML or JCV-GCN, and that the diagnosis and management of GCN should follow the guidance for PML.

Overall, the safety profile of Tyruko is considered to be comparable to that which has been established for the reference biologic drug Tysabri. Appropriate warnings and precautions are in place in the approved Product Monograph for Tyruko to address the identified safety concerns, as is found in the Product Monograph for Tysabri.

Indications

Within this drug submission, the sponsor requested the authorization of Tyruko for the indication granted for Tysabri, the reference biologic drug.

Similarity between Tyruko and Tysabri was established in accordance with the Guidance Document: Information and Submission Requirements for Biosimilar Biologic Drugs.

Importantly, the demonstration of similarity between a proposed biosimilar and its reference biologic drug enables the sponsor’s submission for the proposed biosimilar to rely on the safety and efficacy information already generated for the reference biologic drug.

Upon review of the evidence submitted, including results of structural, functional, non-clinical, and clinical pharmacokinetic, pharmacodynamic, immunogenicity, efficacy, and safety comparisons, Health Canada authorized Tyruko for the same indication held by Tysabri, as follows:

Tyruko (natalizumab for injection) is indicated as monotherapy (i.e., single disease-modifying agent) for the treatment of patients with the relapsing-remitting form of multiple sclerosis (MS) to reduce the frequency of clinical exacerbations, to decrease the number and volume of active brain lesions identified on magnetic resonance imaging (MRI) scans and to delay the progression of physical disability. Tyruko is generally recommended in MS patients who have had an inadequate response to, or are unable to tolerate, other therapies for multiple sclerosis.