GP2015, a proposed etanercept biosimilar: Pharmacokinetic similarity to its reference product and comparison of its autoinjector device with prefilled syringes.

AIMS: To assess pharmacokinetics (PK) and safety of GP2015, a proposed etanercept biosimilar, in two studies: comparison with etanercept originator (ETN, bioequivalence study) and comparison of GP2015 administered via an autoinjector (AI) or prefilled syringes (PFS, delivery study). METHODS: Both studies were randomized, two-sequence, two-period, crossover studies conducted in healthy male subjects. In the bioequivalence study, subjects were randomized to receive a single 50 mg subcutaneous (s.c.) injection of GP2015 or ETN. In the delivery study, subjects were randomized to receive a single 50 mg s.c. injection of GP2015 via AI or PFS. Following a wash-out period of 35 days, subjects in the bioequivalence study received single 50 mg s.c. injection of GP2015 or ETN, and subjects in the delivery study received single 50 mg s.c. injection of GP2015 via AI or PFS. RESULTS: The geometric mean ratios (90% confidence interval) of GP2015/ETN for Cmax (1.11 [1.05-1.17]), AUC0-tlast (0.98 [0.94-1.02]) and AUC0-inf (0.96 [0.93-1.00]) were within the predefined bioequivalence range of 0.80-1.25. The geometric mean ratios (90% confidence interval) of AI/PFS for Cmax (1.01 [0.94-1.08]), AUC0-tlast (1.01 [0.95-1.07]) and AUC0-inf (1.01 [0.96-1.07]) were also within the range 0.80-1.25. No new safety issues were reported. Three subjects had low titres of non-neutralising anti-drug antibodies during a follow-up visit in the bioequivalence study. CONCLUSIONS: The PK of GP2015 was similar to ETN, demonstrating bioequivalence. The safety profile of GP2015 was consistent with previous reports for ETN. The GP2015 AI provided equivalent dosing and tolerability to the GP2015 PFS.

Protein chaperones mediating copper insertion into the CuA site of the aa3-type cytochrome c oxidase of Paracoccus denitrificans.

The biogenesis of the mitochondrial cytochrome c oxidase is a complex process involving the stepwise assembly of its multiple subunits encoded by two genetic systems. Moreover, several chaperones are required to recruit and insert the redox-active metal centers into subunits I and II, two a-type hemes and a total of three copper ions, two of which form the CuA center located in a hydrophilic domain of subunit II. The copper-binding Sco protein(s) have been implicated with the metallation of this site in various model organisms. Here we analyze the role of the two Sco homologues termed ScoA and ScoB, along with two other copper chaperones, on the biogenesis of the cytochrome c oxidase in the bacterium Paracoccus denitrificans by deleting each of the four genes individually or pairwise, followed by assessing the functionality of the assembled oxidase both in intact membranes and in the purified enzyme complex. Copper starvation leads to a drastic decrease of oxidase activity in membranes from strains involving the scoB deletion. This loss is shown to be of dual origin, (i) a severe drop in steady-state oxidase levels in membranes, and (ii) a diminished enzymatic activity of the remaining oxidase complex, traced back to a lower copper content, specifically in the CuA site of the enzyme. Neither of the other proteins addressed here, ScoA or the two PCu proteins, exhibit a direct effect on the metallation of the CuA site in P. denitrificans, but are discussed as potential interaction partners of ScoB.

Pimasertib, a selective oral MEK1/2 inhibitor: absolute bioavailability, mass balance, elimination route, and metabolite profile in cancer patients.

AIM: This trial (NCT: 01713036) investigated the absolute bioavailability, mass balance and metabolite profile of pimasertib in a new design combining these investigations in a single group of patients. METHODS: Six male patients with pathologically confirmed, locally advanced or metastatic solid tumours were enrolled. Exclusion criteria included Eastern Cooperative Oncology Group performance status >1. In Part A of the trial, patients received a 60 mg oral dose of unlabelled pimasertib followed by an intravenous (i.v.) tracer dose of [14 C]pimasertib 2 µg (equalling 9 kBq) as a bolus injection, one hour after the oral dose, on Day 1. On Day 8, all patients received 60 mg pimasertib capsules spiked with 2.6 MBq of [14 C]pimasertib. Patients received 60 mg oral unlabelled pimasertib twice daily from Day 3 to Day 21 of Part A and in subsequent 21-day cycles in Part B. RESULTS: Following i.v. administration, [14 C]pimasertib exhibited a geometric mean total body clearance of 45.7 l h-1 (geometric coefficient of variation [geometric CV]: 47.2%) and a volume of distribution of 229 l (geometric CV: 42.0%). Absolute bioavailability was 73%. The majority of the oral [14 C] dose (85.1%) was recovered in excreta. Total radioactivity was mainly excreted into urine (52.8%) and faeces (30.7%) with 78.9% of the [14 C] dose recovered as metabolites. Two major circulating metabolites were identified in plasma: a carboxylic acid (M445) and a phosphoethanolamine conjugate (M554). The safety profile was in line with the published pimasertib trials. CONCLUSION: Pimasertib showed a favourable pharmacokinetic profile with high absolute bioavailability and a unique metabolic pathway (conjugation with phosphoethanolamine).

Silica nanoparticles for the oriented encapsulation of membrane proteins into artificial bilayer lipid membranes.

An artificial bilayer lipid membrane system is presented, featuring the oriented encapsulation of membrane proteins in a functionally active form. Nickel nitrilo-triacetic acid-functionalized silica nanoparticles, of a diameter of around 25 nm, are used to attach the proteins via a genetically engineered histidine tag in a uniform orientation. Subsequently, the proteins are reconstituted within a phospholipid bilayer, formed around the particles by in situ dialysis to form so-called proteo-lipobeads (PLBs). With a final size of about 50 nm, the PLBs can be employed for UV/vis spectroscopy studies, particularly of multiredox center proteins, because the effects of light scattering are negligible. As a proof of concept, we use cytochrome c oxidase (CcO) from P. denitrificans with the his tag genetically engineered to subunit I. In this orientation, the P side of CcO is directed to the outside and hence electron transfer can be initiated by reduced cytochrome c (cc). UV/vis measurements are used in order to determine the occupancy by CcO molecules encapsulated in the lipid bilayer as well as the kinetics of electron transfer between CcO and cc. The kinetic data are analyzed in terms of the Michaelis-Menten kinetics showing that the turnover rate of CcO is significantly decreased compared to that of solubilized protein, whereas the binding characteristics are improved. The data demonstrate the suitability of PLBs for functional cell-free bioassays of membrane proteins.

Proteo-lipobeads for the oriented encapsulation of membrane proteins.

As a surrogate of live cells, proteo-lipobeads are presented, encapsulating functional membrane proteins in a strict orientation into a lipid bilayer. Assays can be performed just as on live cells, for example using fluorescence measurements. As a proof of concept, we have demonstrated proton transport through cytochrome c oxidase.

The protein effect in the structure of two ferryl-oxo intermediates at the same oxidation level in the heme copper binuclear center of cytochrome c oxidase.

Identification of the intermediates and determination of their structures in the reduction of dioxygen to water by cytochrome c oxidase (CcO) are particularly important to understanding both O2 activation and proton pumping by the enzyme. In this work, we report the products of the rapid reaction of O2 with the mixed valence form (CuA(2+), heme a(3+), heme a3(2+)-CuB(1+)) of the enzyme. The resonance Raman results show the formation of two ferryl-oxo species with characteristic Fe(IV)=O stretching modes at 790 and 804 cm(-1) at the peroxy oxidation level (PM). Density functional theory calculations show that the protein environment of the proximal H-bonded His-411 determines the strength of the distal Fe(IV)=O bond. In contrast to previous proposals, the PM intermediate is also formed in the reaction of Y167F with O2. These results suggest that in the fully reduced enzyme, the proton pumping ν(Fe(IV)=O) = 804 cm(-1) to ν(Fe(IV)=O) = 790 cm(-1) transition (P→F, where P is peroxy and F is ferryl) is triggered not only by electron transfer from heme a to heme a3 but also by the formation of the H-bonded form of the His-411-Fe(IV)=O conformer in the proximal site of heme a3. The implications of these results with respect to the role of an O=Fe(IV)-His-411-H-bonded form to the ring A propionate of heme a3-Asp-399-H2O site and, thus, to the exit/output proton channel (H2O) pool during the proton pumping P→F transition are discussed. We propose that the environment proximal to the heme a3 controls the spectroscopic properties of the ferryl intermediates in cytochrome oxidases.

'Totality of Evidence' Approach in the Development of GP2017, an Approved Adalimumab Biosimilar.

INTRODUCTION: Hyrimoz®, (GP2017 [SDZ-ADL]), is a biosimilar to Humira® (REF-ADL). SDZ-ADL was approved in 2018 by both the United States Food and Drug Administration (US FDA) and European Medicines Agency (EMA) for the indications of REF-ADL not protected by orphan exclusivity. In 2023, the US FDA and EMA also approved a citrate-free high-concentration formulation (HCF) of SDZ-ADL. TOTALITY OF EVIDENCE-THE APPROACH: Approval of SDZ-ADL was based on data gathered using the US FDA, EMA and World Health Organization (WHO)-recommended step-wise Totality of Evidence approach. This approach is a robust dataset confirming high confidence in analytical, functional, pharmacokinetic (PK) and clinical biosimilarity between the biosimilar and reference medicine determined through analytical and clinical investigation. EVIDENCE OF BIOSIMILARITY: Evidence supporting the biosimilarity of SDZ-ADL and REF-ADL was reported at each stage of investigation. Comprehensive comparative analytical and functional assessments demonstrated that SDZ-ADL was analytically indistinguishable from REF-ADL in required critical quality attributes, including receptor binding. Phase I clinical data showed PK similarity of SDZ-ADL and REF-ADL in healthy volunteers, with similar safety, tolerability and immunogenicity profiles. Phase III confirmatory efficacy and safety studies, ADACCESS (included in US/EU dossiers) and ADMYRA (separate to US/EU dossiers), both confirmed that SDZ-ADL's efficacy, safety, and immunogenicity matched REF-ADL in all patient groups with no clinically meaningful differences. More recently, this data package was the basis for a citrate-free HCF of SDZ-ADL to be developed, and its PK, safety and immunogenicity were confirmed against the initially approved formulation of SDZ-ADL. CONCLUSION: Overall, the Totality of Evidence provided for biosimilar adalimumab, SDZ-ADL, confirmed the analytical, functional and clinical similarity of SDZ-ADL to REF-ADL, supporting its regulatory approval and providing a data bridge with which to evaluate and support the approval of citrate-free HCF SDZ-ADL for clinical use.

A biosimilar is a type of medicine that is designed to match the structure and function of a 'reference' biologic medicine. Hyrimoz^® (SDZ-ADL) is a biosimilar of the adalimumab reference medicine, Humira^® ([REF-ADL]). SDZ-ADL was approved in the US and Europe in 2018. For SDZ-ADL to be approved, a collection of evidence needed to be created, called the 'Totality of Evidence.' The purpose of this collection of data is to show there is a high confidence that the new biosimilar medicine matches the reference medicine, from the structure of the medicine to the effect of the medicine on the human body. For SDZ-ADL, this investigation started with comparing the physical structure and other functional properties of SDZ-ADL versus REF-ADL and ended with clinical studies in both healthy volunteers and in patients with diseases treated with adalimumab. This Totality of Evidence gathered for biosimilar adalimumab, SDZ-ADL, confirmed the similarity of SDZ-ADL to REF-ADL and therefore supported the approval of SDZ-ADL. In 2018, a citrate-free high-concentration version (high concentration formulation [HCF]) of REF-ADL was launched that matched REF-ADL. HCF REF-ADL has since become the primary formulation of REF-ADL used in practice. In 2023, a HCF version of SDZ-ADL was also approved in the US and EU based on evidence confirming that HCF SDZ-ADL matched SDZ-ADL. As SDZ-ADL had been previously confirmed to match the reference medicine, this meant that HCF SDZ-ADL could be directly compared against SDZ-ADL to confirm biosimilarity and support its approval.

Signal-to-noise ratio to assess magnitude, kinetics and impact on pharmacokinetics of the immune response to an adalimumab biosimilar.

Background: The antidrug antibody (ADA) signal-to-noise (S/N) ratio was explored as a novel immunogenicity measure to evaluate the immune response of healthy subjects to a single dose of GP2017, an adalimumab biosimilar. Methodology/results: Bioanalytical methods used for the analysis of ADA S/N ratios and ADA titers were validated for sensitivity, precision and drug interference. ADA S/N ratios strongly correlated with ADA titers. Correlations between ADA area under the curve and ADAmax and pharmacokinetics (PK) were stronger for ADA S/N ratio than for ADA titers. Conclusion: ADA S/N ratio allowed for a more sensitive evaluation of the magnitude and kinetics of the immune response, was better correlated with adalimumab PK and was superior to ADA titers in assessing the impact of the immune response on PK.

Introducing the Biosimilar Paradigm to Neurology: The Totality of Evidence for the First Biosimilar Natalizumab.

A biosimilar medicine is a successor to a reference ('originator'/'original-brand') biologic medicine brought to market once the patent and exclusive marketing rights for the reference have expired. Biosimilar natalizumab (PB006 [biosim-NTZ]; developed by Polpharma Biologics S.A. and marketed globally as Tyruko®; Sandoz) has been developed as a successor to reference natalizumab (Tysabri® [ref-NTZ]; Biogen) and is the first US Food and Drug Administration (FDA)-approved and European Medicines Agency (EMA)-approved biosimilar in neurology. As per the FDA and EMA indications for ref-NTZ, biosim-NTZ is approved to treat relapsing forms of multiple sclerosis (USA, EU) and Crohn's disease (USA only). Approval of biosim-NTZ was based on the 'totality of evidence', a comprehensive body of data collected during the development process, demonstrating similarity to its reference medicine. The foundational step of demonstrating structural and functional similarity between biosim-NTZ and ref-NTZ confirmed identical primary and indistinguishable higher order structures, as well as matching binding affinity to α4ß1/α4ß7 integrins. Following the confirmation of matching structure and function, pharmacokinetic/pharmacodynamic similarity of biosim-NTZ to ref-NTZ in healthy subjects was demonstrated, with no clinically meaningful differences identified in safety and immunogenicity. A comparative, double-blind, randomized study (Antelope) was also conducted in patients with relapsing-remitting multiple sclerosis and demonstrated matching efficacy, safety, and immunogenicity with no clinically meaningful differences between biosim-NTZ and ref-NTZ. This review presents the totality of evidence that confirmed the biosimilarity of biosimilar natalizumab to its reference medicine, which supported its approval by the FDA and the EMA. [Graphical plain language summary available].

Allosteric interactions and proton conducting pathways in proton pumping aa(3) oxidases: heme a as a key coupling element.

In this paper allosteric interactions in protonmotive heme aa(3) terminal oxidases of the respiratory chain are dealt with. The different lines of evidence supporting the key role of H(+)/e(-) coupling (redox Bohr effect) at the low spin heme a in the proton pump of the bovine oxidase are summarized. Results are presented showing that the I-R54M mutation in P. denitrificans aa(3) oxidase, which decreases by more than 200mV the E(m) of heme a, inhibits proton pumping. Mutational amino acid replacement in proton channels, at the negative (N) side of membrane-inserted prokaryotic aa(3) oxidases, as well as Zn(2+) binding at this site in the bovine oxidase, uncouples proton pumping. This effect appears to result from alteration of the structural/functional device, closer to the positive, opposite (P) surface, which separates pumped protons from those consumed in the reduction of O(2) to 2 H(2)O.

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.

PB006 (developed by Polpharma Biologics S.A; and marketed as Tyruko® by Sandoz) is an approved biosimilar to the reference medicine, natalizumab (Tysabri®, Biogen [ref-NTZ]) used to treat relapsing forms of multiple sclerosis. Approved biosimilar medicines have been shown to be as safe and effective as their reference medicines via different types of comparisons to the reference medicine, confirming that physicians and patients can expect the same clinical outcome.This study was conducted to confirm that PB006 acts the same way in the body as ref-NTZ. Healthy participants received one dose of either PB006, ref-NTZ from the US or ref-NTZ from Europe. During the study, blood samples were tested to confirm how much of each medicine was present in participants' blood, as well as to assess changes in immune cells or proteins related to how natalizumab works. The study also measured whether any treatment caused unwanted side effects or caused any changes in the immune system that may stop the medicine working.The results showed that PB006 behaved in the same way as ref-NTZ in the blood. All reported side effects were similar between groups and were as expected for this medicine, and neither PB006 nor ref-NTZ caused any important or unexpected changes to the immune system. This study showed that biosimilar natalizumab, PB006, behaves in the same way as ref-NTZ, and the same treatment outcomes can be expected.

GP2017-HCF, a high concentration formulation, demonstrates similar pharmacokinetics, immunogenicity and safety to GP2017, an approved adalimumab biosimilar.

BACKGROUND: GP2017 is an adalimumab biosimilar. The objective of this study is to compare the pharmacokinetics (PK) of GP2017 in its approved formulation and GP2017-high concentration formulation (HCF) in a randomized, double-blind, two-arm PK bridging study. RESEARCH DESIGN AND METHODS: Healthy male subjects received a single 40 mg subcutaneous injection of either GP2017-HCF (n = 162) or GP2017 (n = 168). PK, safety, and immunogenicity were assessed over 72 days post-injection. RESULTS: The 90% confidence intervals [CIs] of geometric mean ratios between GP2017-HCF and GP2017 for Cmax, AUC0-inf, AUC0-360 and AUC0-last were within the pre-defined margin of 0.80 to 1.25; thus, PK comparability between GP2017-HCF and GP2017 was demonstrated. Subgroup analysis of PK comparability by anti-drug antibody (ADA) subpopulation showed that the 90% CIs of geometric mean ratios between GP2017-HCF and GP2017 for Cmax, AUC0-inf, AUC0-360 and AUC0-last were within the margin of 0.80 to 1.25 in ADA-positive and ADA-negative subjects. The proportions of subjects with positive ADA responses and with neutralizing antibodies were comparable between the GP2017-HCF and GP2017 groups. GP2017-HCF and GP2017 were well tolerated, and there were no reports of deaths or other serious adverse events. CONCLUSION: Results show PK comparability between GP2017-HCF and GP2017 and comparable safety and tolerability.

First-in-Human, Single- and Multiple-Ascending-Dose, Food-Effect, and Absolute Bioavailability Trials to Assess the Pharmacokinetics, Safety, and Tolerability of Pritelivir, a Nonnucleoside Helicase-Primase Inhibitor Against Herpes Simplex Virus in Healthy Subjects.

The pharmacokinetics and safety of the novel herpes simplex virus helicase-primase inhibitor pritelivir were evaluated in 5 phase 1 trials: a single-ascending-dose trial, 2 multiple-ascending-dose trials, a food-effect trial, and an absolute bioavailability trial in healthy male subjects. One cohort of healthy female subjects was included in the single-ascending-dose trial. Pritelivir pharmacokinetics were linear up to 480 mg following single and up to 400 mg following multiple once-daily doses. The half-life ranged from 52 to 83 hours, and steady state was reached between 8 and 13 days. Maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last quantifiable concentration were 1.5- and 1.1-fold higher in female compared to male subjects. Absolute bioavailability was 72% under fasted conditions. Following a fatty diet, pritelivir time to maximum concentration was 1.5 hour delayed and maximum plasma concentration and area under the plasma concentration-time curve from time 0 to the last quantifiable concentration were 33% and 16% higher, respectively. Pritelivir was safe and well tolerated up to 600 mg following single and up to 200 mg following multiple once-daily doses. Considering a therapeutic dose of 100 mg once-daily, pritelivir demonstrated a favorable safety and tolerability and pharmacokinetic profile in healthy subjects to support further development.

Clinical evidence of herbal drugs as perpetrators of pharmacokinetic drug interactions.

The use of herbal/botanical products, also referred to as complementary and alternative medicines (CAM), worldwide enjoys increasing popularity. It appears in particular highly prevalent in patient populations already exposed to complex treatment algorithms and polypharmacotherapy, frequently involving narrow therapeutic index drugs. Accordingly, the potential clinical dimension and relevance of herb-drug interactions has received considerable attention over the last years. However, review of pertinent literature indicates that the available clinical evidence in this regard is still limited and sometimes inconclusive. Also, communication of herb-drug interaction data in the biopharmaceutical/medical literature is often complex and confusing, not always unbiased, and in many cases appears not to strive for clear-cut and useful guidance in terms of the clinical relevance of such findings.This systematic review summarizes and interprets the published evidence on clinical herb-drug interaction studies which examined the potential of six popular herbal drugs (Echinacea, garlic, gingko, ginseng, goldenseal, and milk thistle) as perpetrators of pharmacokinetic (PK) drug interactions. Reported effect sizes were systematically categorized according to FDA drug interaction guideline criteria. A total of 66 clinical PK interaction studies, meeting the scope of the present review, were identified. The clinical evidence was found to be most robust and informative for Gingko biloba (GB; 21 studies) and milk thistle/silymarin (MT; 13), and appears still limited for ginseng (9), goldenseal/berberine (GS; 8), garlic (8), and Echinacea (7). Collectively, the available evidence indicates that, at commonly recommended doses, none of these herbs act as potent or moderate inhibitors or inducers of cytochrome P450 (CYP) enzymes or P-glycoprotein (ABCB1). Weak effects in terms of either induction or inhibition were found for GB (presystemic/hepatic CYP3A4 induction/inhibition, CYP2C19 induction at high doses), milk thistle/silymarin (CYP2C9 inhibition), GS/berberine (CYP3A4 and CYP2D6 inhibition), Echinacea (presystemic/hepatic CYP3A4 inhibition/induction, CYP1A2 and CYP2C9 inhibition at high doses). Information was found not always complete for the major drug metabolizing CYP enzymes in the less well-studied herbs and is largely limited to P-glycoprotein (ABCB1) when effects on drug transporters have been investigated.

A novel heme a insertion factor gene cotranscribes with the Thermus thermophilus cytochrome ba3 oxidase locus.

Studying the biogenesis of the Thermus thermophilus cytochrome ba(3) oxidase, we analyze heme a cofactor insertion into this membrane protein complex. Only three proteins linked to oxidase maturation have been described for this extreme thermophile, and in particular, no evidence for a canonical Surf1 homologue, required for heme a insertion, is available from genome sequence data. Here, we characterize the product of an open reading frame, cbaX, in the operon encoding subunits of the ba(3)-type cytochrome c oxidase. CbaX shares no sequence identity with any known oxidase biogenesis factor, and CbaX homologues are found only in the Thermaceae group. In a series of cbaX deletion and complementation experiments, we demonstrate that the resulting ba(3) oxidase complexes, affinity purified via an internally inserted His tag located in subunit I, are severely affected in their enzymatic activities and heme compositions in both the low- and high-spin sites. Thus, CbaX displays typical features of a generic Surf1 factor essential for binding and positioning the heme a moiety for correct assembly into the protein scaffold of oxidase subunit I.

Electron transfer and energy transduction in the terminal part of the respiratory chain - lessons from bacterial model systems.

This review focuses on the terminal part of the respiratory chain where, macroscopically speaking, electron transfer (ET) switches from the two-electron donor, ubiquinol, to the single-electron carrier, cytochrome c, to finally reduce the four-electron acceptor dioxygen. With 3-D structures of prominent representatives of such multi-subunit membrane complexes known for some time, this section of the ET chain still leaves a number of key questions unanswered. The two relevant enzymes, ubiquinol:cytochrome c oxidoreductase and cytochrome c oxidase, appear as rather diverse modules, differing largely in their design for substrate interaction, internal ET, and moreover, in their mechanisms of energy transduction. While the canonical mitochondrial complexes have been investigated for almost five decades, the corresponding bacterial enzymes have been established only recently as attractive model systems to address basic reactions in ET and energy transduction. Lacking the intricate coding background and mitochondrial assembly pathways, bacterial respiratory enzymes typically offer a much simpler subunit composition, while maintaining all fundamental functions established for their complex "relatives". Moreover, related issues ranging from primary steps in cofactor insertion to supramolecular architecture of ET complexes, can also be favourably addressed in prokaryotic systems to hone our views on prototypic structures and mechanisms common to all family members.

Long-term Efficacy, Safety, and Immunogenicity of the Infliximab (IFX) Biosimilar, PF-06438179/GP1111, in Patients with Rheumatoid Arthritis After Switching from Reference IFX or Continuing Biosimilar Therapy: Week 54-78 Data From a Randomized, Double-Blind, Phase III Trial.

OBJECTIVE: Our objective was to evaluate the long-term efficacy, safety, and immunogenicity of the infliximab biosimilar, PF-06438179/GP1111 (PF-SZ-IFX), in patients with rheumatoid arthritis (RA) who continued biosimilar treatment throughout 78 weeks or who switched from reference infliximab (Remicade®) sourced from the EU (IFX-EU) at week 30 or week 54 in the REFLECTIONS B537-02 study. METHODS: In this phase III, double-blind, active-controlled study, patients with moderate-to-severe active RA were initially randomized to PF-SZ-IFX or IFX-EU, each with methotrexate (treatment period [TP] 1; N = 650). At week 30, patients receiving PF-SZ-IFX continued PF-SZ-IFX; patients receiving IFX-EU were re-randomized to continue IFX-EU or switch to PF-SZ-IFX (TP2; n = 566). From weeks 54 to 78, all patients received open-label treatment with PF-SZ-IFX (TP3; n = 505). Efficacy, safety, and immunogenicity data were analyzed during TP3. RESULTS: Efficacy was sustained and comparable across groups at week 78, with American College of Rheumatology criteria for ≥ 20% clinical improvement response rates of 75.9% (biosimilar group), 77.8% (week 30 switch group), and 68.3% (week 54 switch group). The incidence of treatment-emergent adverse events was 28.9%, 29.4%, and 30.2%, respectively. The proportion of patients who were antidrug antibody (ADA) positive and neutralizing antibody positive (as a percentage of ADA-positive patients) was stable and comparable between groups. CONCLUSIONS: Results to week 78 continue to support the efficacy, safety, and immunogenicity of PF-SZ-IFX in patients with moderate-to-severe active RA. There were no clinically meaningful differences between groups, independent of a single treatment transition from IFX-EU to PF-SZ-IFX at week 30 or week 54. TRIAL REGISTRATION NUMBER: NCT02222493.

Effects of rifampicin on the pharmacokinetics of roflumilast and roflumilast N-oxide in healthy subjects.

AIMS: To evaluate the effect of co-administration of rifampicin, an inducer of cytochrome P450 (CYP)3A4, on the pharmacokinetics of roflumilast and roflumilast N-oxide. Roflumilast is an oral, once-daily phosphodiesterase 4 (PDE4) inhibitor, being developed for the treatment of chronic obstructive pulmonary disease. Roflumilast is metabolized by CYP3A4 and CYP1A2, with further involvement of CYP2C19 and extrahepatic CYP1A1. In vivo, roflumilast N-oxide contributes >90% to the total PDE4 inhibitory activity. METHODS: Sixteen healthy male subjects were enrolled in an open-label, three-period, fixed-sequence study. They received a single oral dose of roflumilast 500 microg on days 1 and 12 and repeated oral doses of rifampicin 600 mg once daily on days 5-15. Plasma concentrations of roflumilast and roflumilast N-oxide were measured for up to 96 h. Test/Reference ratios and 90% confidence intervals (CIs) of geometric means for AUC and C(max) of roflumilast and roflumilast N-oxide and for oral apparent clearance (CL/F) of roflumilast were estimated. RESULTS: During the steady-state of rifampicin, the AUC(0-infinity) of roflumilast decreased by 80% (point estimate 0.21; 90% CI 0.16, 0.27); C(max) by 68% (0.32; CI 0.26, 0.39); for roflumilast N-oxide, the AUC(0-infinity) decreased by 56% (0.44; CI 0.36, 0.55); C(max) increased by 30% (1.30; 1.15, 1.48); total PDE4 inhibitory activity decreased by 58% (0.42; 0.38, 0.48). CONCLUSIONS: Co-administration of rifampicin and roflumilast led to a reduction in total PDE4 inhibitory activity of roflumilast by about 58%. The use of potent cytochrome P450 inducers may reduce the therapeutic effect of roflumilast.

A novel screening strategy to identify ABCB1 substrates and inhibitors.

We tested the hypothesis whether data on ABCB1 ATPase activity and passive permeability can be used in combination to identify ABCB1 substrates and inhibitors. We determined passive permeability using an artificial membrane permeability assay (HDM-PAMPA) and ABCB1 function, i.e., vanadate-sensitive ATPase activity for a training set (40 INN drugs) and a validation set (26 development compounds). In parallel experiments, we determined ABCB1 function, i.e., vectorial transport in a Caco-2 cell monolayer, and ABCB1 inhibition, i.e., calcein AM extrusion out of K562-MDR cells, to cross-validate the results with cellular assays. We found that compounds that did not modulate ABCB1-ATPase did also not affect calcein AM extrusion and were not actively transported by ABCB1 in Caco-2 cell monolayers. The results corroborated the effect of passive permeability as an important covariate of active transport: active transport in Caco-2 monolayer was only apparent for compounds showing low passive permeability (<5.0 cmx10(-6)/s) in the HDM-PAMPA assay whereas compounds with high passive permeability (>50 cmx10(-6)/s) were shown to inhibit calcein AM efflux with IC50 values close to their respective Km value obtained for ABCB1-ATPase. The use of HDM-PAMPA in combination with ABCB1-ATPase offers a simple, inexpensive experimental approach capable of identifying ABCB1 inhibitors as well as transported substrates.

Population pharmacokinetics of PF-06438179/GP1111 (an infliximab biosimilar) and reference infliximab in patients with moderately to severely active rheumatoid arthritis.

Background: PF-06438179/GP1111 (PF-SZ-IFX) is an infliximab (IFX) biosimilar. Pharmacokinetic (PK) similarity of PF-SZ-IFX and reference IFX authorized in the European Union (ref-IFX-EU) and in the US (ref-IFX-US) was demonstrated in healthy subjects. Safety and efficacy of PF-SZ-IFX were investigated in a multinational, double-blind, randomized study in rheumatoid arthritis (RA) patients. This work aims to evaluate the population pharmacokinetics (PopPK) of ref-IFX-EU and PF-SZ-IFX in RA patients. Research design and methods: Patients with moderately to severely active RA (N = 650) were randomized 1:1 to PF-SZ-IFX or ref-IFX-EU. PopPK modeling with data collected from the study was performed using a nonlinear mixed-effects approach (NONMEM 7.2.0). Results: The PK of ref-IFX-EU and PF-SZ-IFX were adequately described using a two-compartment model with linear elimination. Clearance (CL) estimates were 0.014 L/h and 0.015 L/h for PF-SZ-IFX and ref-IFX-EU, with inter-individual variability (IIV) on CL of 43.1% and 40.1%, respectively. Volumes of distribution in the central compartment (V1) were 3.38 L and 3.57 L, with IIV on V1 of 28.1% and 23.7%, respectively. The same covariates of sex and antidrug antibody titers on CL, and body weight on V1, influenced the PK variability of ref-IFX-EU and PF-SZ-IFX. Conclusions: PopPK analysis revealed no appreciable differences between the PK of ref-IFX-EU and PF-SZ-IFX in RA patients. Trial registration: The trial is registered at ClinicalTrials.gov (CT.gov identifier: NCT02222493).