A Phase I Study of DLYE5953A, an Anti-LY6E Antibody Covalently Linked to Monomethyl Auristatin E, in Patients with Refractory Solid Tumors.

PURPOSE: DLYE5953A is an antibody-drug conjugate consisting of an anti-LY6E antibody covalently linked to the cytotoxic agent monomethyl auristatin E. This study characterized the safety, pharmacokinetics, immunogenicity, potential biomarkers, and antitumor activity of DLYE5953A in patients with metastatic solid tumors. PATIENTS AND METHODS: This was a phase I, open-label, 3+3 dose-escalation, and dose-expansion study of DLYE5953A administered intravenously every 21 days (Q3W) in patients with locally advanced or metastatic solid malignancies. RESULTS: Sixty-eight patients received DLYE5953A (median, four cycles; range, 1-27). No dose-limiting toxicities were identified during dose escalation (0.2-2.4 mg/kg; n = 20). The recommended phase II dose (RP2D) of 2.4 mg/kg Q3W was based on overall safety and tolerability. Dose-expansion cohorts for HER2-negative metastatic breast cancer (HER2-negative MBC; n = 23) and non-small cell lung cancer (NSCLC; n = 25) patients were enrolled at the RP2D. Among patients receiving DLYE5953A 2.4 mg/kg (n = 55), the most common (≥30%) related adverse events (AEs) included alopecia, fatigue, nausea, and peripheral neuropathy. Grade ≥3 related AEs occurred in 14 of 55 (26%) patients, with neutropenia being the most common (13%). DLYE5953A demonstrated linear total antibody pharmacokinetics at doses of ≥0.8 mg/kg with low unconjugated monomethyl auristatin E levels in blood. Partial response was confirmed in eight of 68 (12%) patients, including three of 29 patients with MBC (10%) and five of 25 patients with NSCLC (20%) at the RP2D. Stable disease was the best response for 37 of 68 (54%) patients. CONCLUSIONS: DLYE5953A administered at 2.4 mg/kg has acceptable safety. Preliminary evidence of antitumor activity in patients with HER2-negative MBC and NSCLC supports further investigation of LY6E as a therapeutic target.

Phase I study of the anti-endothelin B receptor antibody-drug conjugate DEDN6526A in patients with metastatic or unresectable cutaneous, mucosal, or uveal melanoma.

Background Endothelin B receptor (ETBR) is involved in melanoma pathogenesis and is overexpressed in metastatic melanoma. The antibody-drug conjugate DEDN6526A targets ETBR and is comprised of the humanized anti-ETBR monoclonal antibody conjugated to the anti-mitotic agent monomethyl auristatin E (MMAE). Methods This Phase I study evaluated the safety, pharmacokinetics, pharmacodynamics, and anti-tumor activity of DEDN6526A (0.3-2.8 mg/kg) given every 3 weeks (q3w) in patients with metastatic or unresectable cutaneous, mucosal, or uveal melanoma. Results Fifty-three patients received a median of 6 doses of DEDN6526A (range 1-49). The most common drug-related adverse events (>25% across dose levels) were fatigue, peripheral neuropathy, nausea, diarrhea, alopecia, and chills. Three patients in dose-escalation experienced a dose-limiting toxicity (infusion-related reaction, increased ALT/AST, and drug-induced liver injury). Based on cumulative safety data across all dose levels, the recommended Phase II dose (RP2D) for DEDN6526A was 2.4 mg/kg intravenous (IV) q3w. The pharmacokinetics of antibody-conjugated MMAE and total antibody were dose-proportional at doses ranging from 1.8-2.8 mg/kg. A trend toward faster clearance was observed at doses of 0.3-1.2 mg/kg. There were 6 partial responses (11%) in patients with metastatic cutaneous or mucosal melanoma, and 17 patients (32%) had prolonged stable disease ≥6 months. Responses were independent of BRAF mutation status but did correlate with ETBR expression. Conclusion DEDN6526A administered at the RP2D of 2.4 mg/kg q3w had an acceptable safety profile and showed evidence of anti-tumor activity in patients with cutaneous, mucosal, and uveal melanoma. ClinicalTrials.gov identifier: NCT01522664.

Evaluation and use of an anti-cynomolgus monkey CD79b surrogate antibody-drug conjugate to enable clinical development of polatuzumab vedotin.

BACKGROUND AND PURPOSE: Polatuzumab vedotin is an antibody-drug conjugate (ADC) being developed for non-Hodgkin's lymphoma. It contains a humanized anti-CD79b IgG1 monoclonal antibody linked to monomethyl auristatin E (MMAE), an anti-mitotic agent. Polatuzumab vedotin binds to human CD79b only. Therefore, a surrogate ADC that binds to cynomolgus monkey CD79b was used to determine CD79b-mediated pharmacological effects in the monkey and to enable first-in-human clinical trials. EXPERIMENTAL APPROACH: Polatuzumab vedotin, the surrogate ADC, and the corresponding antibodies were evaluated in different assays in vitro and in animals. In vitro assessments included binding to peripheral blood mononuclear cells from different species, binding to a human and monkey CD79b-expressing cell line, binding to human Fcγ receptors, and stability in plasma across species. In vivo, ADCs were assessed for anti-tumour activity in mice, pharmacokinetics/pharmacodynamics in monkeys, and toxicity in rats and monkeys. KEY RESULTS: Polatuzumab vedotin and surrogate ADC bind with similar affinity to human and cynomolgus monkey B cells, respectively. Comparable in vitro plasma stability, in vivo anti-tumour activity, and mouse pharmacokinetics were also observed between the surrogate ADC and polatuzumab vedotin. In monkeys, only the surrogate ADC showed B-cell depletion and B-cell-mediated drug disposition, but both ADCs showed similar MMAE-driven myelotoxicity, as expected. CONCLUSIONS AND IMPLICATIONS: The suitability of the surrogate ADC for evaluation of CD79b-dependent pharmacology was demonstrated, and anti-tumour activity, pharmacokinetics/pharmacodynamics, and toxicity data with both ADCs supported the entry of polatuzumab vedotin into clinical trials.

Immunogenicity of antibody-drug conjugates: observations across 8 molecules in 11 clinical trials.

Aim: To evaluate the clinical immunogenicity of eight antibody-drug conjugates (ADCs), multi-domain biotherapeutics that could theoretically pose a greater immunogenicity risk than monoclonal antibodies (mAbs) because they contain non-natural structural motifs. Methodology & results: Immunogenicity strategies and assays for these ADCs included those commonly used for conventional biotherapeutics with additional characterization. A tiered approach was adopted for testing Phase I and II clinical study samples with screening, confirmatory assays and additional domain characterization. Antidrug antibody incidences with these ADCs were within those reported for mAb biotherapeutics with no apparent impact on clinical outcomes. Conclusion: These data suggest that the ADC hapten-like structure across these eight ADCs does not appear to increase patient immune responses beyond those generally observed for mAb biotherapeutics.

Preclinical and translational pharmacokinetics of a novel THIOMAB™ antibody-antibiotic conjugate against Staphylococcus aureus.

DSTA4637S, a novel THIOMAB™ antibody-antibiotic conjugate (TAC) against Staphylococcus aureus (S. aureus), is currently being investigated as a potential therapy for complicated S. aureus bloodstream infections. DSTA4637S is composed of a monoclonal THIOMABTM IgG1 recognizing S. aureus linked to a rifamycin-class antibiotic (dmDNA31) via a protease-cleavable linker. The pharmacokinetics (PK) of DSTA4637A (a liquid formulation of DSTA4637S) and its unconjugated antibody MSTA3852A were characterized in rats and monkeys. Systemic concentrations of three analytes, total antibody (TAb), antibody-conjugated dmDNA31 (ac-dmDNA31), and unconjugated dmDNA31, were measured to describe complex TAC PK in nonclinical studies. In rats and monkeys, following intravenous administration of a single dose of DSTA4637A, systemic concentration-time profiles of both TAb and ac-dmDNA31 were bi-exponential, characterized by a short distribution phase and a long elimination phase as expected for a monoclonal antibody-based therapeutic. Systemic exposures of both TAb and ac-dmDNA31 were dose proportional over the dose range tested, and ac-dmDNA31 cleared 2-3 times faster than TAb. Unconjugated dmDNA31 plasma concentrations were low (<4 ng/mL) in every study regardless of dose. In this report, an integrated semi-mechanistic PK model for two analytes (TAb and ac-dmDNA31) was successfully developed and was able to well describe the complicated DSTA4637A PK in mice, rats and monkeys. DSTA4637S human PK was predicted reasonably well using this model with allometric scaling of PK parameters from monkey data. This work provides insights into PK behaviors of DSTA4637A in preclinical species and informs clinical translatability of these observed results and further clinical development. Abbreviations: ADC: Antibody-drug conjugate; AUCinf: time curve extrapolated to infinity; ac-dmDNA31: antibody-conjugated dmDNA31; Cmax: maximum concentration observed; DAR: drug-to-antibody ratio; CL: clearance; CLD: distribution clearance; CL1: systemic clearance of all DAR species; kDC: deconjugation rate constant; PK: Pharmacokinetics; IV: Intravenous; IgG: Immunoglobulin G; mAb: monoclonal antibody; S. aureus: Staphylococcus aureus; TAC: THIOMABTM antibody-antibiotic conjugate; TDC: THIOMABTM antibody-drug conjugate; TAb: total antibody; t1/2, λz: terminal half-life; vc linker: valine-citrulline linker; Vss: volume of distribution at steady state; Vc: volume of distribution for the central compartment; Vp: the volume of distribution for the peripheral compartment.

Phase 2 Randomized Trial of the Safety and Efficacy of MHAA4549A, a Broadly Neutralizing Monoclonal Antibody, in a Human Influenza A Virus Challenge Model.

MHAA4549A, a human monoclonal antibody targeting the hemagglutinin stalk region of influenza A virus (IAV), is being developed as a therapeutic for patients hospitalized with severe IAV infection. The safety and efficacy of MHAA4549A were assessed in a randomized, double-blind, placebo-controlled, dose-ranging study in a human IAV challenge model. One hundred healthy volunteers were inoculated with A/Wisconsin/67/2005 (H3N2) IAV and, 24 to 36 h later, administered a single intravenous dose of either placebo, MHAA4549A (400, 1,200, or 3,600 mg), or a standard oral dose of oseltamivir. Subjects were assessed for safety, pharmacokinetics (PK), and immunogenicity. The intent-to-treat-infected (ITTI) population was assessed for changes in viral load, influenza symptoms, and inflammatory biomarkers. MHAA4549A was well tolerated in all IAV challenge subjects. The 3,600-mg dose of MHAA4549A significantly reduced the viral burden relative to that of the placebo as determined by the area under the curve (AUC) of nasopharyngeal virus infection, quantified using quantitative PCR (98%) and 50% tissue culture infective dose (TCID50) (100%) assays. Peak viral load, duration of viral shedding, influenza symptom scores, mucus weight, and inflammatory biomarkers were also reduced. Serum PK was linear with a half-life of ∼23 days. No MHAA4549A-treated subjects developed anti-drug antibodies. In conclusion, MHAA4549A was well tolerated and demonstrated statistically significant and substantial antiviral activity in an IAV challenge model. (This study has been registered at ClinicalTrials.gov under identifier NCT01980966.).

Application of a Plug-and-Play Immunogenicity Assay in Cynomolgus Monkey Serum for ADCs at Early Stages of Drug Development.

Immunogenicity assessment during early stages of nonclinical biotherapeutic development is not always warranted. It is rarely predictive for clinical studies and evidence for the presence of anti-drug antibodies (ADAs) may be inferred from the pharmacokinetic (PK) profile. However, collecting and banking samples during the course of the study are prudent for confirmation and a deeper understanding of the impact on PK and safety. Biotherapeutic-specific ADA assays commonly developed can require considerable time and resources. In addition, the ADA assay may not be ready when needed if the study of PK and safety data triggers assay development. During early stages of drug development for antibody-drug conjugates (ADCs), there is the added complication of the potential inclusion of several molecular variants in a study, differing in the linker and/or drug components. To simplify analysis of ADAs at this stage, we developed plug-and-play generic approaches for both the assay format and the data analysis steps. Firstly, the assay format uses generic reagents to detect ADAs. Secondly, we propose a cut point methodology based on animal specific baseline variability instead of a population data approach. This assay showed good sensitivity, drug tolerance, and reproducibility across a variety of antibody-derived biotherapeutics without the need for optimization across molecules.

Semi-mechanistic Multiple-Analyte Pharmacokinetic Model for an Antibody-Drug-Conjugate in Cynomolgus Monkeys.

PURPOSE: A semi-mechanistic multiple-analyte population pharmacokinetics (PK) model was developed to describe the complex relationship between the different analytes of monomethyl auristatin E (MMAE) containing antibody-drug conjugates (ADCs) and to provide insight regarding the major pathways of conjugate elimination and unconjugated MMAE release in vivo. METHODS: For an anti-CD79b-MMAE ADC the PK of total antibody (Tab), conjugate (evaluated as antibody conjugated MMAE or acMMAE), and unconjugated MMAE were quantified in cynomolgus monkeys for single (0.3, 1, or 3 mg/kg), and multiple doses (3 or 5 mg/kg, every-three-weeks for 4 doses). The PK data of MMAE in cynomolgus monkeys, after intravenous administration of MMAE at single doses (0.03 or 0.063 mg/kg), was included in the analysis. A semi-mechanistic model was developed and parameter estimates were obtained by simultaneously fitting the model to all PK data using a hybrid ITS-MCPEM method. RESULTS: The final model well described the observed Tab, acMMAE and unconjugated MMAE concentration-time profiles. Analysis suggested that conjugate is lost via both proteolytic degradation and deconjugation, while unconjugated MMAE in systemic circulation appears to be mainly released via proteolytic degradation of the conjugate. CONCLUSIONS: Our model improves the understanding of ADC catabolism, which may provide useful insights when designing future ADCs.

DCDT2980S, an anti-CD22-monomethyl auristatin E antibody-drug conjugate, is a potential treatment for non-Hodgkin lymphoma.

Antibody-drug conjugates (ADC), potent cytotoxic drugs linked to antibodies via chemical linkers, allow specific targeting of drugs to neoplastic cells. We have used this technology to develop the ADC DCDT2980S that targets CD22, an antigen with expression limited to B cells and the vast majority of non-Hodgkin lymphomas (NHL). DCDT2980S consists of a humanized anti-CD22 monoclonal IgG1 antibody with a potent microtubule-disrupting agent, monomethyl auristatin E (MMAE), linked to the reduced cysteines of the antibody via a protease cleavable linker, maleimidocaproyl-valine-citrulline-p-aminobenzoyloxycarbonyl (MC-vc-PAB). We describe the efficacy, safety, and pharmacokinetics of DCDT2980S in animal models to assess its potential as a therapeutic for the treatment of B-cell malignancies. We did not find a strong correlation between in vitro or in vivo efficacy and CD22 surface expression, nor a correlation of sensitivity to free drug and in vitro potency. We show that DCDT2980S was capable of inducing complete tumor regression in xenograft mouse models of NHL and can be more effective than rituximab plus combination chemotherapy at drug exposures that were well tolerated in cynomolgus monkeys. These results suggest that DCDT2980S has an efficacy, safety, and pharmacokinetics profile that support potential treatment of NHL.