Anti-neuropilin-1 (MNRP1685A): unexpected pharmacokinetic differences across species, from preclinical models to humans

Endothelial Neuropilin-1: a multifaced signal transducer with an emerging role in inflammation and atherosclerosis beyond angiogenesis

Neuropilin-1 (NRP1) is a transmembrane glycoprotein expressed by several cell types including, neurons, endothelial cells (ECs), smooth muscle cells, cardiomyocytes and immune cells comprising macrophages, dendritic cells and T cell subsets. Since NRP1 discovery in 1987 as an adhesion molecule in the frog nervous system, more than 2300 publications on PubMed investigated the function of NRP1 in physiological and pathological contexts. NRP1 has been characterised as a coreceptor for class 3 semaphorins and several members of the vascular endothelial growth factor (VEGF) family. Because the VEGF family is the main regulator of blood and lymphatic vessel growth in addition to promoting neurogenesis, neuronal patterning, neuroprotection and glial growth, the role of NRP1 in these biological processes has been extensively investigated. It is now established that NRP1 promotes the physiological growth of new vessels from pre-existing ones in the process of angiogenesis. Furthermore, several studies have shown that NRP1 mediates signalling pathways regulating pathological vascular growth in ocular neovascular diseases and tumour development. Less defined are the roles of NRP1 in maintaining the function of the quiescent established vasculature in an adult organism. This review will focus on the opposite roles of NRP1 in regulating transforming growth factor β signalling pathways in different cell types, and on the emerging role of endothelial NRP1 as an atheroprotective, anti-inflammatory factor involved in the response of ECs to shear stress.

Neuropilin-1 is essential for vascular endothelial growth factor A-mediated increase of sensory neuron activity and development of pain-like behaviors

ABSTRACT

Neuropilin-1 (NRP-1) is a transmembrane glycoprotein that binds numerous ligands including vascular endothelial growth factor A (VEGFA). Binding of this ligand to NRP-1 and the co-receptor, the tyrosine kinase receptor VEGFR2, elicits nociceptor sensitization resulting in pain through the enhancement of the activity of voltage-gated sodium and calcium channels. We previously reported that blocking the interaction between VEGFA and NRP-1 with the Spike protein of SARS-CoV-2 attenuates VEGFA-induced dorsal root ganglion (DRG) neuronal excitability and alleviates neuropathic pain, pointing to the VEGFA/NRP-1 signaling as a novel therapeutic target of pain. Here, we investigated whether peripheral sensory neurons and spinal cord hyperexcitability and pain behaviors were affected by the loss of NRP-1. Nrp-1 is expressed in both peptidergic and nonpeptidergic sensory neurons. A CRIPSR/Cas9 strategy targeting the second exon of nrp-1 gene was used to knockdown NRP-1. Neuropilin-1 editing in DRG neurons reduced VEGFA-mediated increases in CaV2.2 currents and sodium currents through NaV1.7. Neuropilin-1 editing had no impact on voltage-gated potassium channels. Following in vivo editing of NRP-1, lumbar dorsal horn slices showed a decrease in the frequency of VEGFA-mediated increases in spontaneous excitatory postsynaptic currents. Finally, intrathecal injection of a lentivirus packaged with an NRP-1 guide RNA and Cas9 enzyme prevented spinal nerve injury-induced mechanical allodynia and thermal hyperalgesia in both male and female rats. Collectively, our findings highlight a key role of NRP-1 in modulating pain pathways in the sensory nervous system.

Non-human primates in the PKPD evaluation of biologics: Needs and options to reduce, refine, and replace. A BioSafe White Paper

Monoclonal antibodies (mAbs) deliver great benefits to patients with chronic and/or severe diseases thanks to their strong specificity to the therapeutic target. As a result of this specificity, non-human primates (NHP) are often the only preclinical species in which therapeutic antibodies cross-react with the target. Here, we highlight the value and limitations that NHP studies bring to the design of safe and efficient early clinical trials. Indeed, data generated in NHPs are integrated with in vitro information to predict the concentration/effect relationship in human, and therefore the doses to be tested in first-in-human trials. The similarities and differences in the systems defining the pharmacokinetics and pharmacodynamics (PKPD) of mAbs in NHP and human define the nature and the potential of the preclinical investigations performed in NHPs. Examples have been collated where the use of NHP was either pivotal to the design of the first-in-human trial or, inversely, led to the termination of a project prior to clinical development. The potential impact of immunogenicity on the results generated in NHPs is discussed. Strategies to optimize the use of NHPs for PKPD purposes include the addition of PD endpoints in safety assessment studies and the potential re-use of NHPs after non-terminal studies or cassette dosing several therapeutic agents of interest. Efforts are also made to reduce the use of NHPs in the industry through the use of in vitro systems, alternative in vivo models, and in silico approaches. In the case of prediction of ocular PK, the body of evidence gathered over the last two decades renders the use of NHPs obsolete. Expert perspectives, advantages, and pitfalls with these alternative approaches are shared in this review.

Novel In Vivo and In Vitro Pharmacokinetic/Pharmacodynamic-Based Human Starting Dose Selection for Glofitamab

We present a novel approach for first-in-human (FIH) dose selection of the CD20xCD3 bispecific antibody, glofitamab, based on pharmacokinetic/pharmacodynamic (PKPD) assessment in cynomolgus monkeys to select a high, safe starting dose, with cytokine release (CR) as the PD endpoint. Glofitamab pharmacokinetics were studied in mice and cynomolgus monkeys; PKPD of IL-6, TNF-α and interferon-γ release following glofitamab, with/without obinutuzumab pretreatment (Gpt) was studied in cynomolgus monkeys. Potency differences for CR between cynomolgus monkeys and humans were determined by glofitamab incubation in whole blood of both species. The PKPD model for CR was translated to humans to project a starting dose that did not induce CR exceeding a clinically-predefined threshold. In cynomolgus monkeys, glofitamab showed a species-specific atypical high clearance, with and without B-cell debulking by Gpt. CR was related to glofitamab serum levels and B-cell counts. B-cell reduction by Gpt led to a marked decrease in CR. FIH starting dose (5 µg) was selected based on IL-6 release considering the markedly higher glofitamab in vitro potency in human vs monkey blood. This is a novel PKPD-based approach for selection of FIH starting dose for a CD20xCD3 bispecific antibody in B-cell lymphoma, evidenced in the glofitamab study, NP30179 (NCT03075696).

A Single Animal Species-Based Prediction of Human Clearance and First-in-Human Dose of Monoclonal Antibodies: Beyond Monkey

These days, there is a lot of emphasis on the prediction of human clearance (CL) from a single species for monoclonal antibodies (mabs). Many studies indicate that monkey is the most suitable species for the prediction of human clearance for mabs. However, it is not well established if rodents (mouse or rat) can also be used to predict human CL for mabs. The objectives of this study were to predict and compare human CL as well as first-in-human dose of mabs from mouse or rat, ormonkey. Four methods were used for the prediction of human CL of mabs. These methods were: use of four allometric exponents (0.75, 0.80, 0.85, and 0.90), a minimal physiologically based pharmacokinetics method (mPBPK), lymph flow rate, and liver blood flow rate. Based on the predicted CL, first-in-human dose of mabs was projected using either exponent 1.0 (linear scaling) or exponent 0.85, and human-equivalent dose (HED) from each of these species. The results of the study indicated that rat or mouse could provide a reasonably accurate prediction of human CL as well as first-in-human dose of mabs. When exponent 0.85 was used for CL prediction, there were 78%, 95%, and 92% observations within a 2-fold prediction error for mouse, rat, and monkey, respectively. Predicted human dose fell within the observed human dose range (administered to humans) for 10 out of 13 mabs for mouse, 11 out of 12 mabs for rat, and 12 out of 15 mabs for monkey. Overall, the clearance and first-in-human dose of mabs were predicted reasonably well by all three species (a single species). On average, monkey may be the best species for the prediction of human clearance and human dose but mouse or rat especially; rat can be a very useful species for conducting the aforementioned studies.

Pharmacokinetic prediction of an antibody in mice based on an in vitro cell-based approach using target receptor-expressing cells

In vivo pharmacokinetics (PK) studies using mice and monkeys are the main approaches for evaluating and predicting the PK of antibodies, and there is a strong demand for methods that do not require animal experiments. In this work, we focused on quantitatively predicting the nonlinear PK of an antibody based on cell-based assays. An anti-mouse Fc gamma receptor IIB antibody was used as a model antibody. To determine the PK parameters related to nonspecific elimination in vivo, the plasma concentration profile at 100 mg/kg, at which target-specific clearance is saturated, was analyzed by a 2-compartment model. To estimate the parameters related to target-specific elimination, the Michaelis–Menten constant (K_m) and the maximum elimination rate (V_max) were determined by an uptake assay using Chinese hamster ovary (CHO) cells expressing the target receptor. Finally, the integration of all of these parameters permitted the PK to be predicted at doses ranging from 1 to 100 mg/kg regardless of whether target-specific clearance was saturated or nonsaturated. The findings presented herein show that in vitro assays using target-expressing cells are useful tools for obtaining PK parameters and predicting PK profiles and, in some cases, eliminate the need for in vivo PK studies using experimental animals.

Population pharmacokinetic analysis of phase 1 bemarituzumab data to support phase 2 gastroesophageal adenocarcinoma FIGHT trial

Purpose

To report population pharmacokinetic (PK) analysis of the phase 1 study (FPA144-001, NCT02318329) and to select a clinical dose and schedule that will achieve an empirical target trough concentration (C_trough) for an anti-fibroblast growth factor receptor 2b antibody, bemarituzumab.

Methods

Nonlinear mixed-effect modeling was used to analyse PK data. In vitro binding affinity and receptor occupancy of bemarituzumab were determined. Simulation was conducted to estimate dose and schedule to achieve an empirical target C_trough in a phase 2 trial (FIGHT, NCT03694522) for patients receiving first-line treatment combined with modified 5-fluourouracil, oxaliplatin and leucovorin (mFOLFOX6) for gastric and gastroesophageal junction adenocarcinoma.

Results

Bemarituzumab PK is best described by a two-compartment model with parallel linear and nonlinear (Michaelis–Menten) elimination from the central compartment. Albumin, gender, and body weight were identified as the covariates on the linear clearance and/or volume of distribution in the central compartment, and no dose adjustment was warranted. An empirical target of bemarituzumab C_trough of ≥ 60 µg/mL was projected to achieve > 95% receptor occupancy based on in vitro data. Fifteen mg/kg every 2 weeks, with a single dose of 7.5 mg/kg on Cycle 1 Day 8, was projected to achieve the target C_trough on Day 15 in 98% of patients with 96% maintaining the target at steady state, which was confirmed in the FIGHT trial.

Conclusion

A projected dose and schedule to achieve the target C_trough was validated in phase 1 of the FIGHT trial which supported selection of the phase 2 dose and schedule for bemarituzumab.

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04139-4) contains supplementary material, which is available to authorized users.

Antibody-Drug Conjugates as Cancer Therapeutics: Past, Present, and Future

Antibody-drug conjugates (ADCs) represent an innovative therapeutic approach that provides novel treatment options and hope for patients with cancer. By coupling monoclonal antibodies (mAbs) to cytotoxic small-molecule payloads with a plasma-stable linker, ADCs offer the potential for increased drug specificity and fewer off-target effects than systemic chemotherapy. As evidence for the potential of these therapies, many new ADCs are in various stages of clinical development. Because their structure poses unique challenges to pharmacokinetic and pharmacodynamic characterization, it is critical to recognize the differences between ADCs and conventional chemotherapy in the design of ADC clinical development strategies. Although some properties may be determined mainly by either the mAb or the small-molecule portion, the behavior of these agents is not always predictable. Furthermore, because the absorption, distribution, metabolism, and excretion (ADME) of ADCs are influenced by all 3 of its components (mAb, linker, and payload), it is important to characterize the intact molecule, any target-mediated catabolic clearance of the mAb, and the ADME properties of the small-molecule payload. Here we describe key issues in the clinical development of ADCs, including considerations for designing first-in-human studies for ADCs. We discuss some difficulties of ADC pharmacokinetic characterization and current approaches to overcoming these challenges. Finally, we consider all aspects of clinical pharmacology assessment required during drug development, using examples from the literature to illustrate the discussion.

Structure-activity relationship study of a small cyclic peptide H-c[Lys-Pro-Glu]-Arg-OH: a potent inhibitor of Vascular Endothelial Growth Factor interaction with Neuropilin-1

Inhibition of angiogenesis is one of the most promising approaches in anticancer therapy. It was recently suggested that Neuropilin-1 (NRP-1) in tumour cells may serve as a separate receptor for Vascular Endothelial Growth Factor-165 (VEGF₁₆₅) which is one of the main pro-angiogenic agents in the organism. Therefore molecules inhibiting VEGF₁₆₅ binding to NRP-1 could be potential candidates for new antiangiogenic and anticancer drugs. Here we present a structure-activity relationship study of the peptide H-c[Lys-Pro-Glu]-Arg-OH which showed high inhibitory effect on VEGF₁₆₅/NRP-1 binding (IC₅₀=0.18μM) in our previous study. We report the design, synthesis, in vitro assays and docking analysis of four small cyclic peptides (14-,15-membered ring) and one bigger cyclic compound (30-membered ring). Our study shows that both the ring size and configuration of amino acid residues present in the structure are crucial for high inhibitory effect.

Translational pharmacokinetics and pharmacodynamics of monoclonal antibodies

Monoclonal antibodies (mAbs) are an important therapeutic class with complex pharmacology and interdependent pharmacokinetic (PK) and pharmacodynamics (PD) properties. Understanding the PK and PD of mAbs and their biological and mechanistic underpinnings are crucial in enabling their design and selection, designing appropriate efficacy and toxicity studies, translating PK/PD parameters to humans, and optimizing dose and regimen to maximize success in the clinic. Significant progress has been made in this field however many critical questions still remain. This article gives a brief overview of the PK and PD of mAbs, factors that influence them, and areas of ongoing inquiry. Current tools and translational approaches to predict the PK/PD of mAbs in humans are also discussed.

NRP1 function and targeting in neurovascular development and eye disease

Neuropilin 1 (NRP1) is expressed by neurons, blood vessels, immune cells and many other cell types in the mammalian body and binds a range of structurally and functionally diverse extracellular ligands to modulate organ development and function. In recent years, several types of mouse knockout models have been developed that have provided useful tools for experimental investigation of NRP1 function, and a multitude of therapeutics targeting NRP1 have been designed, mostly with the view to explore them for cancer treatment. This review provides a general overview of current knowledge of the signalling pathways that are modulated by NRP1, with particular focus on neuronal and vascular roles in the brain and retina. This review will also discuss the potential of NRP1 inhibitors for the treatment for neovascular eye diseases.

Immunoglobulin Fc-fused, neuropilin-1-specific peptide shows efficient tumor tissue penetration and inhibits tumor growth via anti-angiogenesis

Neuropilin-1 (NRP1) receptor, involved in vascular endothelial growth factor (VEGF)-mediated vascular permeability and tumor angiogenesis, is targeted by peptides that bind to its VEGF-binding site. However, these peptides also cross-react with the structurally related receptor, NRP2. Here, we describe an immunoglobulin Fc-fused peptide, Fc-TPP11, which specifically binds to the VEGF-binding site of NRP1 with approximately 2nM affinity, but negligibly to that of NRP2. Fc-TPP11 triggered NRP1-dependent signaling, enhanced vascular permeability via vascular endothelial (VE)-cadherin downregulation, and increased paracellular permeability via E-cadherin downregulation in tumor tissues. Fc-TPP11 also significantly enhanced the tumor penetration of co-injected anti-cancer drug, doxorubicin, leading to the improved in vivo anti-tumor efficacy. Fc-TPP11 was easily adapted to the full-length anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb) cetuximab (Erbitux), cetuximab-TPP11, exhibiting more than 2-fold improved tumor penetration than the parent cetuximab. Fc-TPP11 exhibited a similar whole-body half-life to that of intact Fc in tumor bearing mice. In addition to the tumor-penetrating activity, Fc-TPP11 suppressed VEGF-dependent angiogenesis by blocking VEGF binding to NRP1, thereby inhibiting tumor growth without promoting metastasis in the mouse model. Our results show that NRP1-specific, high-affinity binding of Fc-TPP11, is useful to validate NRP1 signaling, independent of NRP2. Thus, Fc-TPP11 can be used as a tumor penetration-promoting agent with anti-angiogenic activity or directly adapted to mAb-TPP11 format for more potent anti-cancer antibody therapy.

Challenges and advances in the assessment of the disposition of antibody-drug conjugates

Antibody‐drug conjugates (ADCs) are a rapidly growing therapeutic platform for the treatment of cancer. ADCs consist of a cytotoxic small molecule drug linked to an antibody to provide targeted delivery of the cytotoxic agent to the tumor. Understanding the pharmacokinetics (PK) and pharmacodynamics (PD) of ADCs is crucial in their design to optimize dose and regimen, to maximize efficacy and to minimize toxicity in patients. Significant progress has been made in recent years in this area, however, many fundamental questions still remain. This review discusses factors to consider while assessing the disposition of ADCs, and the unique challenges associated with these therapeutics. Current tools that are available and strategies to enable appropriate assessment are also discussed. © 2015 Genentech Inc. Biopharmaceutics & Drug Disposition Published by John Wiley & Sons Ltd.

A Phase Ib study evaluating MNRP1685A, a fully human anti-NRP1 monoclonal antibody, in combination with bevacizumab and paclitaxel in patients with advanced solid tumors

PURPOSE

MNRP1685A is a human monoclonal antibody that blocks binding of vascular endothelial growth factor (VEGF), VEGF-B, and placental growth factor 2 to neuropilin-1 resulting in vessel immaturity and VEGF dependency. The safety of combining MNRP1685A with bevacizumab, with or without paclitaxel, was examined.

METHODS

Patients with advanced solid tumors received escalating doses of MNRP1685A (7.5, 15, 24, and 36 mg/kg) with bevacizumab 15 mg/kg every 3 weeks in Arm A (n = 14). Arm B (n = 10) dosing consisted of MNRP1685A (12 and 16 mg/kg) with bevacizumab 10 mg/kg (every 2 weeks) and paclitaxel 90 mg/m(2) (weekly, 3 of 4 weeks). Objectives were to determine safety, pharmacokinetics, pharmacodynamics, and the maximum tolerated dose of MNRP1685A.

RESULTS

Infusion reactions (88 %) and transient thrombocytopenia (67 %) represent the most frequent study drug-related adverse events (AEs). Drug-related Grade 2 or 3 proteinuria occurred in 13 patients (54 %). Additional study drug-related AEs occurring in >20 % of patients included neutropenia, alopecia, dysphonia, fatigue, and nausea. Neutropenia occurred only in Arm B. Grade ≥3 study drug-related AEs in ≥3 patients included neutropenia (Arm B), proteinuria, and thrombocytopenia. Two confirmed and three unconfirmed partial responses were observed.

CONCLUSIONS

The safety profiles were consistent with the single-agent profiles of all study drugs. However, a higher than expected rate of clinically significant proteinuria was observed that does not support further testing of MNRP1685A in combination with bevacizumab.

A phase I study of the human monoclonal anti-NRP1 antibody MNRP1685A in patients with advanced solid tumors

The human monoclonal antibody MNRP1685A targets the VEGF binding domain of neuropilin-1 (NRP1), a multi-domain receptor necessary for neural development and blood vessel maturation. In nonclinical studies, MNRP1685A prevents vascular maturation by keeping blood vessels in an immature, highly VEGF-dependent state. We explored the safety and tolerability of MNRP1685A in patients with advanced solid tumors. Patients were treated with MNRP1685A given intravenously every 3 weeks using a 3 + 3 dose-escalation design with 7 dose-escalation cohorts. Twenty-four of 35 patients (69 %) experienced drug-related adverse events (AEs) of infusion-related reaction on the day of MNRP1685A administration. With premedication including dexamethasone, infusions were well-tolerated with main symptoms of pruritus and rash. Outside the day of infusion, most common (≥ 2 patients) related AEs were fatigue (17 %), pruritus (9 %), myalgia and thrombocytopenia (both 6 %) (all were Grade 1-2). MNRP1685A-related Grade ≥ 3 AEs consisted of one dose-limiting toxicity of Grade 3 upper gastrointestinal bleeding and one related Grade 3 thrombocytopenia, coinciding with unrelated Grade 3 fungemia and duodenal obstruction. MNRP1685A showed nonlinear PK with more-than-dose proportional increases in exposure, consistent with broad target expression. Transient platelet count reductions (≥ 30 % from predose) were observed in 56 % of evaluable patients. Nine patients were on study for ≥ 4 cycles, one colorectal cancer patient for one year. MNRP1685A was generally well-tolerated. The primary MNRP1685A-related AE was infusion-related reaction, which were attenuated by premedication including dexamethasone. Transient platelet count reductions were frequent but did not impact MNRP1685A dosing.

VEGF targets the tumour cell

The function of vascular endothelial growth factor (VEGF) in cancer is not limited to angiogenesis and vascular permeability. VEGF-mediated signalling occurs in tumour cells, and this signalling contributes to key aspects of tumorigenesis, including the function of cancer stem cells and tumour initiation. In addition to VEGF receptor tyrosine kinases, the neuropilins are crucial for mediating the effects of VEGF on tumour cells, primarily because of their ability to regulate the function and the trafficking of growth factor receptors and integrins. This has important implications for our understanding of tumour biology and for the development of more effective therapeutic approaches.

Population pharmacokinetic analysis from phase I and phase II studies of the humanized monovalent antibody, onartuzumab (MetMAb), in patients with advanced solid tumors

Onartuzumab is a unique, humanized, monovalent (one-armed) monoclonal antibody (mAb) against the MET receptor. The intravenous (IV) pharmacokinetics (PK) of onartuzumab were investigated in a phase I study and a phase II study in recurrent non-small cell lung cancer (NSCLC) patients. The potential for drug-drug interaction (DDI) was assessed during co-administration of IV onartuzumab with oral erlotinib, by measuring the PK of both drugs. The concentration-time profiles of onartuzumab were adequately described using a two-compartment model with linear clearance (CL) at doses between 4 and 30 mg/kg. The estimates for CL, central compartment volume (V1 ), and median terminal half-life were 0.439 L/day, 2.77 L, and 13.4 days, respectively. Statistically significant covariates included creatinine clearance (CrCL) on clearance, weight and gender on V1 , and weight on peripheral compartment volume (V2 ), but the clinical relevance of these covariates needs to be further evaluated. The current analysis did not indicate obvious DDI between onartuzumab and erlotinib. MET diagnostic status did not impact the exposure of either agent. Despite the slightly faster clearance compared with typical bivalent mAbs, the PK of onartuzumab support dosing regimens of 15 mg/kg every 3 weeks or doses equivalent to achieve the target minimum tumoristatic concentration in patients.

Generation and characterization of a unique reagent that recognizes a panel of recombinant human monoclonal antibody therapeutics in the presence of endogenous human IgG

Pharmacokinetic (PK) and immunohistochemistry (IHC) assays are essential to the evaluation of the safety and efficacy of therapeutic monoclonal antibodies (mAb) during drug development. These methods require reagents with a high degree of specificity because low concentrations of therapeutic antibody need to be detected in samples containing high concentrations of endogenous human immunoglobulins. Current assay reagent generation practices are labor-intensive and time-consuming. Moreover, these practices are molecule-specific and so only support one assay for one program at a time. Here, we describe a strategy to generate a unique assay reagent, 10C4, that preferentially recognizes a panel of recombinant human mAbs over endogenous human immunoglobulins. This "panel-specific" feature enables the reagent to be used in PK and IHC assays for multiple structurally-related therapeutic mAbs. Characterization revealed that the 10C4 epitope is conformational, extensive and mainly composed of non-CDR residues. Most key contact residues were conserved among structurally-related therapeutic mAbs, but the combination of these residues exists at low prevalence in endogenous human immunoglobulins. Interestingly, an indirect contact residue on the heavy chain of the therapeutic appears to play a critical role in determining whether or not it can bind to 10C4, but has no affect on target binding. This may allow us to improve the binding of therapeutic mAbs to 10C4 for assay development in the future. Here, for the first time, we present a strategy to develop a panel-specific reagent that can expedite the development of multiple clinical assays for structurally-related therapeutic mAbs.

Design of a cyclotide antagonist of neuropilin-1 and -2 that potently inhibits endothelial cell migration

Neuropilin-1 and -2 are critical regulators of angiogenesis, lymphangiogenesis, and cell survival as receptors for multiple growth factors. Disulfide-rich peptides that antagonize the growth factor receptors neuropilin-1 and neuropilin-2 were developed using bacterial display libraries. Peptide ligands specific for the VEGFA binding site on neuropilin-1 were identified by screening a library of disulfide-rich peptides derived from the thermostable, protease-resistant cyclotide kalata B1. First generation ligands were subjected to one cycle of affinity maturation to yield acyclic peptides with affinities of 40-60 nM and slow dissociation rate constants (∼1 × 10(-3) s(-1)). Peptides exhibited equivalent affinities for human and mouse neuropilin-1 and cross-reacted with human neuropilin-2 with lower affinity. A C-to-N cyclized variant (cyclotide) of one neuropilin ligand retained high affinity, exhibited increased protease resistance, and conferred improved potency for inhibiting endothelial cell migration in vitro (EC50 ≈ 100 nM). These results demonstrate that potent, target-specific cyclotides can be created by evolutionary design and that backbone cyclization can confer improved pharmacological properties.

Population pharmacokinetic and pharmacodynamic modeling of MNRP1685A in cynomolgus monkeys using two-target quasi-steady-state (QSS) model

MNRP1685A (anti-NRP1) is a fully human IgG1 monoclonal antibody against neuropilin-1 (NRP1), a protein necessary for blood vessel maturation. MNRP1685A binds to free membrane-bound NRP1 (mNRP1) and circulating NRP1 (cNRP1). Total cNRP1 increased in a dose-dependent manner following anti-NRP1 administration in mice, rats, and monkeys. The purpose of this study is to develop a mechanism-based model to simultaneously describe the kinetics of both unbound drug (MNRP1685A) and total cNRP1 in cynomolgus monkeys. Pharmacokinetic (PK) and pharmacodynamic (PD) profiles after single- or multiple-dose administrations were well described by the two-target quasi-steady-state (QSS) model. The estimated nonspecific clearance was 3.26 mL/day/kg and central compartment volume was 38.2 mL/kg. The maximum elimination rate for mNRP1-mediated disposition was 98.8 nM/day. The synthesis rate (3.8 nM/day), degradation rate constant (1.53 day(-1)), and complex elimination rate constant (0.260 day(-1)) for cNRP1 were also derived from the model. QSS constants were 6.94 nM for mNRP1 and 2.8 nM for cNRP1. The results suggest that cNRP1 has minimal effect on MNRP1685A PK while mNRP1 plays a major role in the target-mediated drug disposition. This finding is favorable as the desired pharmacological target is mNRP1, rather than cNRP1. The two-target QSS model provides mechanistic understanding of the nonlinear PK of MNRP1685A. Based on the model prediction, the free drug concentrations to maintain free mNRP1 and cNRP1 below 10% of baseline level are 10 and 20 μg/mL, respectively. This serves as a target concentration for clinical dose selection, assuming cynomolgus monkeys are predictive for humans.