The McCAVE Trial: Vanucizumab plus mFOLFOX-6 Versus Bevacizumab plus mFOLFOX-6 in Patients with Previously Untreated Metastatic Colorectal Carcinoma (mCRC).

BACKGROUND: Bevacizumab, a VEGF-A inhibitor, in combination with chemotherapy, has proven to increase progression-free survival (PFS) and overall survival in multiple lines of therapy of metastatic colorectal cancer (mCRC). The angiogenic factor angiopoetin-2 (Ang-2) is associated with poor prognosis in many cancers, including mCRC. Preclinical models demonstrate improved activity when inhibiting both VEGF-A and Ang-2, suggesting that the dual VEGF-A and Ang-2 blocker vanucizumab (RO5520985 or RG-7221) may improve clinical outcomes. This phase II trial evaluated the efficacy of vanucizumab plus modified (m)FOLFOX-6 (folinic acid (leucovorin), fluorouracil (5-FU) and oxaliplatin) versus bevacizumab/mFOLFOX-6 for first-line mCRC. PATIENTS AND METHODS: All patients received mFOLFOX-6 and were randomized 1:1 to also receive vanucizumab 2,000 mg or bevacizumab 5 mg/kg every other week. Oxaliplatin was given for eight cycles; other agents were continued until disease progression or unacceptable toxicity for a maximum of 24 months. The primary endpoint was investigator-assessed PFS. RESULTS: One hundred eighty-nine patients were randomized (vanucizumab, n = 94; bevacizumab, n = 95). The number of PFS events was comparable (vanucizumab, n = 39; bevacizumab, n = 43). The hazard ratio was 1.00 (95% confidence interval, 0.64-1.58; p = .98) in a stratified analysis based on number of metastatic sites and region. Objective response rate was 52.1% and 57.9% in the vanucizumab and bevacizumab arm, respectively. Baseline plasma Ang-2 levels were prognostic in both arms but not predictive for treatment effects on PFS of vanucizumab. The incidence of adverse events of grade ≥3 was similar between treatment arms (83.9% vs. 82.1%); gastrointestinal perforations (10.8% vs. 8.4%) exceeded previously reported rates in this setting. Hypertension and peripheral edema were more frequent in the vanucizumab arm. CONCLUSION: Vanucizumab/mFOLFOX-6 did not improve PFS and was associated with increased rates of antiangiogenic toxicity compared with bevacizumab/mFOLFOX-6. Our results suggest that Ang-2 is not a relevant therapeutic target in first-line mCRC. IMPLICATIONS FOR PRACTICE: This randomized phase II study demonstrates that additional angiopoietin-2 (Ang-2) inhibition does not result in superior benefit over anti-VEGF-A blockade alone when each added to standard chemotherapy. Moreover, the performed pharmacokinetic and pharmacodynamic analysis revealed that vanucizumab was bioavailable and affected its intended target, thereby strongly suggesting that Ang-2 is not a relevant therapeutic target in the clinical setting of treatment-naïve metastatic colorectal cancer. As a result, the further clinical development of the dual VEGF-A and Ang-2 inhibitor vanucizumab was discontinued.

Optimizing Early Clinical Investigations in Cancer Immunotherapy: The Translational Journey of RG6292, a Novel, Selective Treg-Depleting Antibody.

The multifaceted IL-2/IL-2R biology and its modulation by promising therapeutic agents are highly relevant topics in the cancer immunotherapy field. A novel CD25-Treg-depleting antibody (Vopikitug, RG6292) has been engineered to preserve IL-2 signaling on effector T cells to enhance effector activation and antitumor immunity, and is currently being evaluated in the clinic. The Entry into Human-enabling framework described here investigated the characteristics of RG6292, from in vitro quantification of CD25 and RG6292 pharmacology using human tissues to in vivo assessment of PK/PD/safety relationships in cynomolgus monkeys as non-human primate species (NHP). Fundamental knowledge on CD25 and Treg biology in healthy and diseased tissues across NHP and human highlighted the commonalities between these species in regard to the target biology and demonstrated the conservation of RG6292 properties between NHP and human. The integration of in vitro and in vivo PK/PD/safety data from these species enabled the identification of human relevant safety risks, the selection of the most appropriate safe starting dose and the projection of the pharmacologically-relevant dose range. The first clinical data obtained for RG6292 in patients verified the appropriateness of the described approaches as well as validated the full clinical relevance of the projected safety, PK, and PD profiles from animal to man. This work shows how the integration of mechanistic non-clinical data increases the predictive value for human, allowing efficient transition of drug candidates and optimizations of early clinical investigations.

Safety, Pharmacokinetics, Pharmacodynamics, and Antitumor Activity from a Phase I Study of Simlukafusp Alfa (FAP-IL2v) in Advanced/Metastatic Solid Tumors.

PURPOSE: Simlukafusp alfa [fibroblast activation protein α-targeted IL2 variant (FAP-IL2v)], a tumor-targeted immunocytokine, comprising an IL2 variant moiety with abolished CD25 binding fused to human IgG1, is directed against fibroblast activation protein α. This phase I, open-label, multicenter, dose-escalation, and extension study (NCT02627274) evaluated the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of FAP-IL2v in patients with advanced/metastatic solid tumors. PATIENTS AND METHODS: Participants received FAP-IL2v intravenously once weekly. Dose escalation started at 5 mg; flat dosing (≤25 mg) and intraparticipant uptitration regimens (15/20, 20/25, 20/20/35, and 20/35/35 mg) were evaluated. Primary objectives were dose-limiting toxicities, maximum tolerated dose, recommended expansion dose, and pharmacokinetics. RESULTS: Sixty-one participants were enrolled. Dose-limiting toxicities included fatigue (flat dose 20 mg: n = 1), asthenia (25 mg: n = 1), drug-induced liver injury (uptitration regimen 20/25 mg: n = 1), transaminase increase (20/25 mg: n = 1), and pneumonia (20/35/35 mg: n = 1). The uptitration regimen 15/20 mg was determined as the maximum tolerated dose and was selected as the recommended expansion dose. Increases in peripheral blood absolute immune cell counts were seen for all tested doses [NK cells, 13-fold; CD4+ T cells (including regulatory T cells), 2-fold; CD8+ T cells, 3.5-fold] but without any percentage change in regulatory T cells. Clinical activity was observed from 5 mg [objective response rate, 5.1% (n = 3); disease control rate, 27.1% (n = 16)]. Responses were durable [n = 3, 2.8 (censored), 6.3, and 43.4 months]. CONCLUSIONS: FAP-IL2v had a manageable safety profile and showed initial signs of antitumor activity in advanced/metastatic solid tumors.

Industry Perspective on First-in-Human and Clinical Pharmacology Strategies to Support Clinical Development of T-Cell Engaging Bispecific Antibodies for Cancer Therapy.

T-cell-engaging bispecific antibodies (TCEs) that target tumor antigens and T cells have shown great promise in treating cancer, particularly in hematological indications. The clinical development of TCEs often involves a lengthy first-in-human (FIH) trial with many dose-escalation cohorts leading up to an early proof of concept (POC), enabling either a no-go decision or dose selection for further clinical development. Multiple factors related to the target, product, disease, and patient population influence the efficacy and safety of TCEs. The intricate mechanism of action limits the translatability of preclinical models to the clinic, thereby posing challenges to streamline clinical development. In addition, unlike traditional chemotherapy, the top dose and recommended phase II doses (RP2Ds) for TCEs in the clinic are often not guided by the maximum tolerated dose (MTD), but rather based on the integrated dose-response assessment of the benefit/risk profile. These uncertainties pose complex challenges for translational and clinical pharmacologists (PK/PD scientists), as well as clinicians, to design an efficient clinical study that guides development. To that end, experts in the field, under the umbrella of the American Association of Pharmaceutical Scientists, have reviewed learnings from published literature and currently marketed products to share perspectives on the FIH and clinical pharmacology strategies to support early clinical development of TCEs.

Phase 2 study of the antitumour activity and safety of simlukafusp alfa (FAP-IL2v) combined with atezolizumab in patients with recurrent and/or metastatic cervical squamous cell carcinoma.

BACKGROUND: Simlukafusp alfa (FAP-IL2v) is an immune cytokine engineered to selectively promote immune responses in the tumour microenvironment. We evaluated the antitumour activity and safety of FAP-IL2v plus atezolizumab in recurrent and/or metastatic cervical squamous cell carcinoma (SCC) in a phase 2 basket study (NCT03386721). METHODS: Patients with confirmed metastatic, persistent or recurrent cervical SCC who had progressed on ≥1 anti-cancer therapy and had measurable disease were enrolled. FAP-IL2v 10 mg was administered once every 3 weeks (Q3W) or once weekly (QW) for 4 weeks then once every 2 weeks (Q2W) with the corresponding Q3W or Q2W atezolizumab regimens. The primary endpoint was objective response rate by investigator assessment. FINDINGS: Forty-eight patients were enrolled (Q3W: n = 47; QW/Q2W: n = 1). Among 45 response evaluable patients, objective responses occurred in 12 patients (27%; CI 16.0-41.0), including 3 complete and 9 partial responses. Responses occurred in 6/19 PD-L1 positive patients (32%; 95% CI 15.4-54.0) and 5/24 PD-L1 negative patients (21%; 95% CI 9.2-35.6). Median duration of response was 13.3 months (95% CI 7.6-NE). Median progression-free survival was 3.7 months (95% CI 3.3-9.0). Adverse events (AEs) were consistent with the known safety profile of each drug. AEs leading to withdrawal of either agent occurred in 6 patients (13%). Pronounced expansion and activation of natural killer and CD8 T cells in peripheral blood and increased tumour infiltration and inflammation were observed. INTERPRETATION: FAP-IL2v plus atezolizumab is clinically active and has manageable safety in patients with recurrent and/or metastatic cervical SCC. FUNDING: F. Hoffmann-La Roche Ltd.

Phase 1b Study of the Immunocytokine Simlukafusp alfa (FAP-IL2v), in Combination with Cetuximab in Patients with Head and Neck Squamous Cell Carcinoma.

PURPOSE: This phase 1b trial evaluated FAP-IL2v, a novel immune-cytokine engineered to minimize CD25-mediated toxicities, in combination with cetuximab, in patients with recurrent, unresectable, or metastatic head and neck squamous cell carcinoma (HNSCC). PATIENTS AND METHODS: Patients received FAP-IL2v either on a continuous weekly (QW) schedule, or QW for 4 weeks and then every 2 weeks (Q2W). Cetuximab was dosed at QW or Q2W schedules. The primary objectives were to evaluate the safety and tolerability, maximum tolerated dose (MTD), pharmacokinetics, and clinical activity for the combination of FAP-IL2v with cetuximab. Exploratory objectives included pharmacodynamic analyses. RESULTS: A total of 58 patients were enrolled, 19 patients into the dose-escalation, and 39 patients into the expansion part. The MTD of FAP-IL2v was defined as 10 mg (QW/Q2W) in combination with cetuximab (500 mg/m2, Q2W), which was further tested in the expansion part. The most common FAP-IL2v-related adverse events with a grade 3 or 4 severity were hypophosphatemia (19%), lymphopenia (16%), and infusion-related reaction (14%). The pharmacokinetics of FAP-IL2v in combination with cetuximab was similar to that after administration as monotherapy. Consistent with the proposed mode-of-action, FAP-IL2v preferentially expanded intratumoral NK and CD8 T cells. Four patients achieved a partial response, the objective response rate was 7% (95% CI: 3.2, 14.7). CONCLUSIONS: The safety profile of FAP-IL2v in combination with cetuximab was acceptable and pharmacodynamic markers support the proposed mode-of-action of this combination, but the overall low antitumor activity does not warrant further clinical exploration in HNSCC. [Part C of Study BP29842 (NCT02627274).].

Phase II Study to Determine the Antitumor Activity and Safety of Simlukafusp Alfa (FAP-IL2v) Combined with Atezolizumab in Esophageal Cancer.

PURPOSE: In this study, we report the results from the esophageal squamous cell carcinoma (SCC) cohort of a phase II, noncomparative, basket study evaluating the antitumor activity and safety of fibroblast activation protein-IL2 variant (FAP-IL2v) plus atezolizumab in patients with advanced/metastatic solid tumors (NCT03386721). PATIENTS AND METHODS: Eligible patients had an Eastern Cooperative Oncology Group performance status of 0 to 1; measurable metastatic, persistent, or recurrent esophageal SCC; progression on ≥1 prior therapy; and were checkpoint inhibitor-naïve. Patients received FAP-IL2v 10 mg plus atezolizumab 1,200 mg intravenously every 3 weeks, or FAP-IL2v weekly for 4 weeks and then every 2 weeks plus atezolizumab 840 mg intravenously every 2 weeks. The primary endpoint was investigator-assessed objective response rate (ORR). RESULTS: In the response-evaluable population (N = 34), the best confirmed ORR was 20.6% [95% confidence interval (CI), 10.4-36.8], with a complete response seen in 1 patient and partial responses in 6 patients. The disease control rate was 44.1% (complete response = 2.9%; partial response = 17.6%; stable disease = 23.5%), and the median duration of response was 10.1 mon/ths (95% CI, 5.6-26.7). The median progression-free survival was 1.9 months (95% CI, 1.8-3.7). Analysis of response by PDL1 expression (Ventana SP263) resulted in an ORR of 26.7% for patients with PDL1-positive tumors (tumor area positivity cutoff ≥1%; n = 15) and 7.1% for patients with PDL1-negative tumors (tumor area positivity cutoff <1%; n = 14). Overall, the treatment combination was tolerable, and adverse events were consistent with the known safety profiles of each drug. CONCLUSIONS: FAP-IL2v plus atezolizumab demonstrated clinical activity and was tolerable in patients with previously treated esophageal SCC.

Obinutuzumab Pretreatment as a Novel Approach to Mitigate Formation of Anti-Drug Antibodies Against Cergutuzumab Amunaleukin in Patients with Solid Tumors.

PURPOSE: The immunocytokine cergutuzumab amunaleukin (CEA-IL2v) showed manageable safety and favorable pharmacodynamics in phase I/Ib trials in patients with advanced/metastatic carcinoembryonic antigen-positive (CEA+) solid tumors, but this was accompanied by a high incidence of anti-drug antibodies (ADA). We examined B-cell depletion with obinutuzumab as a potential mitigation strategy. EXPERIMENTAL DESIGN: Preclinical data comparing B-cell depletion with rituximab versus obinutuzumab are summarized. Substudies of phase I/Ib trials investigated the effect of obinutuzumab pretreatment on ADA development, safety, pharmacodynamics, and antitumor activity of CEA-IL2v ± atezolizumab in patients with advanced/metastatic or unresectable CEA+ solid tumors who had progressed on standard of care. RESULTS: Preclinical data showed superior B-cell depletion with obinutuzumab versus rituximab. In clinical studies, patients received CEA-IL2v monotherapy with (n = 16) or without (n = 6) obinutuzumab pretreatment (monotherapy study), or CEA-IL2v + atezolizumab + obinutuzumab pretreatment (n = 5; combination study). In the monotherapy study, after four cycles (every 2 weeks treatment), 0/15 evaluable patients administered obinutuzumab pretreatment had ADAs versus 4/6 patients without obinutuzumab. Obinutuzumab pretreatment with CEA-IL2v monotherapy showed no new safety signals and pharmacodynamic data suggested minimal impact on T cells and natural killer cells. Conversely, increased liver toxicity was observed in the combination study (CEA-IL2v + atezolizumab + obinutuzumab pretreatment). CONCLUSIONS: These preliminary findings suggest that obinutuzumab pretreatment before CEA-IL2v administration in patients with CEA+ solid tumors may be a feasible and potent ADA mitigation strategy, with an acceptable safety profile, supporting broader investigation of obinutuzumab pretreatment for ADA mitigation in other settings.

Src/lck inhibitor dasatinib reversibly switches off cytokine release and T cell cytotoxicity following stimulation with T cell bispecific antibodies.

BACKGROUND: T cell engagers are bispecific antibodies recognizing, with one moiety, the CD3ε chain of the T cell receptor and, with the other moiety, specific tumor surface antigens. Crosslinking of CD3 upon simultaneous binding to tumor antigens triggers T cell activation, proliferation and cytokine release, leading to tumor cell killing. Treatment with T cell engagers can be associated with safety liabilities due to on-target on-tumor, on-target off-tumor cytotoxic activity and cytokine release syndrome (CRS). Tyrosine kinases such as SRC, LCK or ZAP70 are involved in downstream signaling pathways after engagement of the T cell receptor and blocking these kinases might serve to abrogate T cell activation when required (online supplemental material 1). Dasatinib was previously identified as a potent kinase inhibitor that switches off CAR T cell functionality. METHODS: Using an in vitro model of target cell killing by human peripheral blood mononuclear cells, we assessed the effects of dasatinib combined with 2+1 T cell bispecific antibodies (TCBs) including CEA-TCB, CD19-TCB or HLA-A2 WT1-TCB on T cell activation, proliferation and target cell killing measured by flow cytometry and cytokine release measured by Luminex. To determine the effective dose of dasatinib, the Incucyte system was used to monitor the kinetics of TCB-mediated target cell killing in the presence of escalating concentrations of dasatinib. Last, the effects of dasatinib were evaluated in vivo in humanized NSG mice co-treated with CD19-TCB. The count of CD20+ blood B cells was used as a readout of efficacy of TCB-mediated killing and cytokine levels were measured in the serum. RESULTS: Dasatinib concentrations above 50 nM prevented cytokine release and switched off-target cell killing, which were subsequently restored on removal of dasatinib. In addition, dasatinib prevented CD19-TCB-mediated B cell depletion in humanized NSG mice. These data confirm that dasatinib can act as a rapid and reversible on/off switch for activated T cells at pharmacologically relevant doses as they are applied in patients according to the label. CONCLUSION: Taken together, we provide evidence for the use of dasatinib as a pharmacological on/off switch to mitigate off-tumor toxicities or CRS by T cell bispecific antibodies.

CD25-Treg-depleting antibodies preserving IL-2 signaling on effector T cells enhance effector activation and antitumor immunity.

Intratumoral regulatory T cell (Treg) abundance associates with diminished anti-tumor immunity and poor prognosis in human cancers. Recent work demonstrates that CD25, the high affinity receptor subunit for IL-2, is a selective target for Treg depletion in mouse and human malignancies; however, anti-human CD25 antibodies have failed to deliver clinical responses against solid tumors due to bystander IL-2 receptor signaling blockade on effector T cells, which limits their anti-tumor activity. Here we demonstrate potent single-agent activity of anti-CD25 antibodies optimized to deplete Tregs whilst preserving IL-2-STAT5 signaling on effector T cells, and demonstrate synergy with immune checkpoint blockade in vivo. Pre-clinical evaluation of an anti-human CD25 (RG6292) antibody with equivalent features demonstrates, in both non-human primates and humanized mouse models, efficient Treg depletion with no overt immune-related toxicities. Our data supports the clinical development of RG6292 and evaluation of novel combination therapies incorporating non-IL-2 blocking anti-CD25 antibodies in clinical studies.

Prediction of the Optimal Dosing Regimen Using a Mathematical Model of Tumor Uptake for Immunocytokine-Based Cancer Immunotherapy.

Purpose: Optimal dosing is critical for immunocytokine-based cancer immunotherapy to maximize efficacy and minimize toxicity. Cergutuzumab amunaleukin (CEA-IL2v) is a novel CEA-targeted immunocytokine. We set out to develop a mathematical model to predict intratumoral CEA-IL2v concentrations following various systemic dosing intensities.Experimental Design: Sequential measurements of CEA-IL2v plasma concentrations in 74 patients with solid tumors were applied in a series of differential equations to devise a model that also incorporates the peripheral concentrations of IL2 receptor-positive cell populations (i.e., CD8+, CD4+, NK, and B cells), which affect tumor bioavailability of CEA-IL2v. Imaging data from a subset of 14 patients were subsequently utilized to additionally predict antibody uptake in tumor tissues.Results: We created a pharmacokinetic/pharmacodynamic mathematical model that incorporates the expansion of IL2R-positive target cells at multiple dose levels and different schedules of CEA-IL2v. Model-based prediction of drug levels correlated with the concentration of IL2R-positive cells in the peripheral blood of patients. The pharmacokinetic model was further refined and extended by adding a model of antibody uptake, which is based on drug dose and the biological properties of the tumor. In silico predictions of our model correlated with imaging data and demonstrated that a dose-dense schedule comprising escalating doses and shortened intervals of drug administration can improve intratumoral drug uptake and overcome consumption of CEA-IL2v by the expanding population of IL2R-positive cells.Conclusions: The model presented here allows simulation of individualized treatment plans for optimal dosing and scheduling of immunocytokines for anticancer immunotherapy. Clin Cancer Res; 24(14); 3325-33. ©2018 AACRSee related commentary by Ruiz-Cerdá et al., p. 3236.

First-in-Human Phase I Study of Single-agent Vanucizumab, A First-in-Class Bispecific Anti-Angiopoietin-2/Anti-VEGF-A Antibody, in Adult Patients with Advanced Solid Tumors.

Purpose: Vanucizumab is an investigational antiangiogenic, first-in-class, bispecific mAb targeting VEGF-A and angiopoietin-2 (Ang-2). This first-in-human study evaluated the safety, pharmacokinetics, pharmacodynamics, and antitumor activity of vanucizumab in adults with advanced solid tumors refractory to standard therapies.Experimental Design: Patients received escalating biweekly (3-30 mg/kg) or weekly (10-30 mg/kg) intravenous doses guided by a Bayesian logistic regression model with overdose control.Results: Forty-two patients were treated. One dose-limiting toxicity, a fatal pulmonary hemorrhage from a large centrally located mediastinal mass judged possibly related to vanucizumab, occurred with the 19 mg/kg biweekly dose. Arterial hypertension (59.5%), asthenia (42.9%), and headache (31%) were the most common toxicities. Seventeen (41%) patients experienced treatment-related grade ≥3 toxicities. Toxicity was generally higher with weekly than biweekly dosing. A MTD of vanucizumab was not reached in either schedule. Pharmacokinetics were dose-linear with an elimination half-life of 6-9 days. All patients had reduced plasma levels of free VEGF-A and Ang-2; most had reductions in KTRANS (measured by dynamic contrast-enhanced MRI). Two patients (renal cell and colon cancer) treated with 30 mg/kg achieved confirmed partial responses. Ten patients were without disease progression for ≥6 months. A flat-fixed 2,000 mg biweekly dose (phamacokinetically equivalent to 30 mg/kg biweekly) was recommended for further investigation.Conclusions: Biweekly vanucizumab had an acceptable safety and tolerability profile consistent with single-agent use of selective inhibitors of the VEGF-A and Ang/Tie2 pathway. Vanucizumab modulated its angiogenic targets, impacted tumor vascularity, and demonstrated encouraging antitumor activity in this heterogeneous population. Clin Cancer Res; 24(7); 1536-45. ©2017 AACR.

Effects of Cytochrome P450 3A4 Inhibitors-Ketoconazole and Erythromycin-on Bitopertin Pharmacokinetics and Comparison with Physiologically Based Modelling Predictions.

OBJECTIVE: To assess the effect of strong and moderate cytochrome P450 (CYP) 3A4 inhibition on exposure of bitopertin, a glycine reuptake inhibitor primarily metabolized by CYP3A4, and to compare the results with predictions based on physiologically based pharmacokinetic (PBPK) modelling. METHODS: The effects of ketoconazole and erythromycin were assessed in two male volunteer studies with open-label, two-period, fixed-sequence designs. Twelve subjects were enrolled in each of the studies. In period 1, a single dose of bitopertin was administered; in period 2, 400 mg ketoconazole was administered once daily for 17 days or 500 mg erythromycin was administered twice daily for 21 days. A single dose of bitopertin was coadministered on day 5. Pharmacokinetic parameters were derived by non-compartmental methods. Simulated bitopertin profiles using dynamic PBPK modelling for a typical healthy volunteer in GastroPlus(®) were used to predict changes in pharmacokinetic parameters. RESULTS: In healthy volunteers, coadministration of ketoconazole increased the bitopertin area under the plasma concentration-time curve (AUC) from 0 to 312 h (AUC0-312h) 4.2-fold (90 % confidence interval [CI] 3.5-5.0) and erythromycin increased the AUC from time zero to infinity (AUC0-inf) 2.1-fold (90 % CI 1.9-2.3). The peak concentration (C max) increased by <25 % in both studies. Simulated bitopertin profiles using PBPK modelling showed good agreement with the observed AUC ratios in both studies. The predicted AUC0-inf ratios for the interaction with ketoconazole and erythromycin were 7.7 and 1.9, respectively. CONCLUSION: Strong CYP3A4 inhibitors increase AUC0-inf of bitopertin 7- to 8-fold and hence should not be administered concomitantly with bitopertin. Moderate CYP3A4 inhibitors double AUC0-inf.

Effects of the glycine reuptake inhibitors bitopertin and RG7118 on glycine in cerebrospinal fluid: results of two proofs of mechanism studies in healthy volunteers.

RATIONALE: Hypofunction of NMDA receptors has been implicated in neuropsychiatric disorders including schizophrenia. NMDA receptor neurotransmission can be enhanced through inhibition of glycine reuptake by the glycine transporter type 1 (GlyT1). OBJECTIVES: The primary objective of these studies was to explore the relationship between plasma exposure and glycine cerebrospinal fluid (CSF) concentrations following administration of bitopertin and RG7118 in healthy volunteers. METHODS: The bitopertin study comprised four dose levels (3, 10, 30 and 60 mg) administered once daily for 10 days. In the RG7118 study, placebo, 15 or 30 mg RG7118 was administered once daily for 28 days. CSF samples were taken on day -2 and day 10, and day -1 and day 26 for bitopertin and RG7118, respectively. RESULTS: Twenty-two and 24 subjects participated in the bitopertin and RG7118 study, respectively. In the bitopertin study, CSF glycine concentrations showed a dose-dependent increase from baseline to day 10. The geometric mean ratios (coefficient of variation) of AUC0-12 h on day 10 over baseline were 1.3 (17 %), 1.3 (49 %), 1.7 (18 %) and 2.3 (14 %) after 3, 10, 30 and 60 mg, respectively. In the RG7118 study, the geometric mean ratio of glycine concentration (CV) on day 26 at 6 h post-dose over time-matched baseline was approx. 1.9 (24 and 15 %) for 15 and 30 mg. CONCLUSIONS: The mechanism of action of bitopertin and RG7118, i.e. inhibition of glycine reuptake in the brain, was confirmed. The maximal increase observed in healthy volunteers was similar to the one observed in animals showing the good translatability of this biomarker.

Physiologically based absorption modelling to predict the impact of drug properties on pharmacokinetics of bitopertin.

Bitopertin (RG1678) is a glycine reuptake inhibitor in phase 3 trials for treatment of schizophrenia. Its clinical oral pharmacokinetics is sensitive to changes in drug substance particle size and dosage form. Physiologically based pharmacokinetic (PBPK) absorption model simulations of the impact of changes in particle size and dosage form (either capsules, tablets, or an aqueous suspension) on oral pharmacokinetics was verified by comparison to measured plasma concentrations. Then, a model parameter sensitivity analysis was applied to set limits on the particle sizes included in tablets for the market. The model was also used to explore the in vitro to in vivo correlation. Simulated changes in oral pharmacokinetics caused by differences in particle size and dosage form were confirmed in two separate relative bioavailability studies. Model parameter sensitivity analyses predicted that AUCinf was hardly reduced as long as particle diameter (D50) remained smaller than 30 µm, and >20% reduced Cmax is anticipated only when particle diameter exceeds 15 µm. An exploration of the sensitivity to the presence of larger particles within a polydisperse distribution showed that simulated Cmax is again more affected than AUC but is less than 20% reduced as long as D50 is less than 8 µm and D90 is smaller than 56 µm. PBPK absorption modelling can contribute to a quality by design (QbD) approach for clinical formulation development and support the setting of biorelevant specifications for release of the product.