Assessment of translational risk in drug research: Role of biomarker classification and mechanism-based PKPD concepts

Pharmacokinetic and pharmacodynamic similarity of biosimilar natalizumab (PB006) to its reference medicine: a randomized controlled trial

BACKGROUND

PB006 (Polpharma Biologics S.A; marketed as Tyruko®, Sandoz) is an approved biosimilar to natalizumab (Tysabri®; Biogen [ref-NTZ]). This multicenter, double-blind, randomized, single-dose study was conducted to demonstrate pharmacokinetic/pharmacodynamic (PK/PD) similarity between PB006 and ref-NTZ.

RESEARCH DESIGN AND METHODS

Healthy participants (N = 453) were randomized to receive 3 mg/kg infusion of PB006, US-licensed, or EU-approved ref-NTZ before an 85-day follow-up. Primary PK endpoint was total natalizumab serum concentration over time; secondary PK endpoints explored concentration changes. Primary PD endpoints compared CD19+ cell counts and percentage α4-integrin receptor saturation, per natalizumab's mechanism of action. Secondary PD endpoints explored serum changes in sVCAM-1 and sMAdCAM-1, CD34+, and CD19+ cells. Safety, tolerability, and immunogenicity were assessed.

RESULTS

The primary PK endpoint was met, with 90% confidence intervals (CIs) of the geometric mean for serum test/reference ratios contained within a prespecified margin (0.8-1.25). All primary PD endpoints were met, with 90% and 95% CIs within this similarity margin for baseline-adjusted CD19+ cell counts and percentage α4-integrin receptor saturation. All secondary endpoints were similarly contained, except sVCAM. No notable differences in safety, tolerability, or immunogenicity were observed.

CONCLUSION

Similarity was confirmed, with PB006 demonstrating PK/PD behavior consistent with that of ref-NTZ.

CLINICAL TRIAL REGISTRATION

EudraCT number 2019-003874-15.

Developing new treatments in partnership for primary mitochondrial disease: What does industry need from academics, and what do academics need from industry?

Developing novel therapeutics for primary mitochondrial disease is likely to require significant academia-industry collaboration. Translational assessments, a tool often used in industry at target validation stage, can highlight disease specific development challenges which requires focused collaborative effort. For PMD, definition of pivotal trial populations and primary endpoints is challenging given lack of clinical precedence, high numbers of subgroups with overlapping symptoms despite common genetics. Disease pathophysiology has not been systematically assessed simultaneously with outcomes in available natural history studies, resulting in a lack of pathophysiology biomarker utilization in clinical trials. Preclinical model systems are available to assist drug development efforts, although these may require better standardization and access. Multistakeholder precompetitive efforts have been used to progress disease pathophysiology biomarker and confirmatory clinical trial endpoint readiness in neurological disease with limited treatment options, such as rare familial Parkinson's disease. This type of approach may be beneficial for PMD therapeutic development, although requires significant funding and time, supported by industry and other funding bodies. Industry expertise on chemistry, data quality and drug development know-how is available to support academic drug development efforts. A combination of industry mindset-reduction of uncertainty to provide an indication statement supportable by evidence-together with academic approach-question-based studies to understand disease mechanisms and patients-has great potential to deliver novel PMD therapeutics.

Evaluation of Therapeutic Equivalence for the Follow-On Version of Intravenously Administered Non-Biological Complex Drugs

The interchangeability evaluation for generic drugs formulated as intravenous injections normally only requires assessments of pharmaceutical equivalence (PE) when the medicinal products are simple small-molecule drugs. However, intravenously administered non-biological complex drugs (NBCDs), such as liposomes, microsphere suspension, or fat emulsion, have inherent passive disposition selectivity due to their special formulations, thereby the in vivo drug performances are improved. Because of the complexity in formulation, the in vitro pharmaceutical investigations of follow-on NBCDs are more complicated than those required for generic small-molecule drugs. In addition to qualitative and quantitative sameness of the active and inactive ingredients, it is required to comparatively study the static and kinetic microscopic particle-related physiochemical properties of the follow-on NBCDs versus the reference products. Moreover, for complex formulations that have a significant impact on the biodistribution of the drug compound, an in vivo bioequivalence (BE) study is also important. Since NBCDs that demonstrated bioequivalence through the conventional BE approach have been found inequivalent in efficacy or safety to the reference products, pivotal BE studies for follow-on NBCDs are required to take both encapsulated/total drug and free drug as the analytes to address release kinetics and biodistribution of the active pharmacological ingredient in the body. This manuscript reviews the 26 U.S. FDA published product-specific guidelines for intravenous injections. In general, these NBCDs can be stratified into four groups according to their release kinetics and ability of bio-membrane penetration. Group 1 consists of seven small-molecule, non-complex drugs; group 2 included four NBCDs with either microscale particle size or rapid dissolution property; group 3 include five loosely packed NBCDs (fat emulsions) and one quickly released ophthalmic liposomal drug; and the last group contains four cytotoxic liposomal or protein-bound NBCDs and five iron carbohydrate complexes. The requirements of the corresponding guidelines range from simple proof of PE between the test and the reference products, to a collection of studies that demonstrate the key manufacturing process (e.g. liposome loading), the particle- or vehicle-wise static and kinetic physiological characterizations, the dissolution test, and BE evaluation of both total/encapsulated drug form and free drug form between the follow-on NBCDs and their reference products. Such studies are challenging in implementation. Therefore, a variety of alternative approaches are proposed in this article.

Pharmacokinetic-Pharmacodynamic Modeling of Brain Dopamine Levels Based on Dopamine Transporter Occupancy after Administration of Methylphenidate in Rats

Dopamine exerts various effects including movement coordination and reward. It is useful to understand the quantitative relationship between drug pharmacokinetics and target engagement such as the change in occupancy and dopamine level in brain for the proper treatment of dopamine-related diseases. This study was aimed at developing a pharmacokinetic-pharmacodynamic (PK-PD) model based on dopamine transporter (DAT) occupancies that could describe changes in extracellular dopamine levels in brain after administration of methylphenidate (a DAT inhibitor) to rat. First, uptake of fluorescent substrates was studied in DAT-expressing human embryonic kidney 293 cells and concentration dependently inhibited by methylphenidate. By analyzing the uptake of fluorescent substrates in the presence or absence of methylphenidate, a mathematical model could estimate the association and dissociation rate constants of methylphenidate for DAT. Next, we measured the concentrations of methylphenidate in plasma and cerebrospinal fluid (CSF) and extracellular dopamine levels in the nucleus accumbens after single intraperitoneal administration of methylphenidate. The concentrations of methylphenidate in plasma increased almost dose proportionally and the CSF-to-plasma concentration ratio was similar among evaluated dose. The extracellular dopamine levels also increased with dose. These data were analyzed using the mechanism-based PK-PD model, which incorporates dopamine biosynthesis, release from a synapse, reuptake via DAT into a synapse, and elimination from a synapse. Methylphenidate concentrations in plasma and dopamine profiles predicted by the PK-PD model were close to in vivo observations. In conclusion, our mechanism-based PK-PD model can accurately describe dopamine levels in the brain after administration of methylphenidate to rats.