Mechanistic Projection of First‐in‐Human Dose for Bispecific Immunomodulatory P‐Cadherin LP‐DART: An Integrated PK/PD Modeling Approach

Abstract

A bispecific immunomodulatory biotherapeutic molecule (P-cadherin LP-DART) based on the Dual Affinity Re-Targeting (DART) scaffold has been developed as a potential antitumor treatment showing efficacy in preclinical testing. A minimal anticipated biological effect level (MABEL) approach was applied to project the first-in-human (FIH) dose, because of its immune agonistic properties following target engagement. The pharmacological activity of P-cadherin LP-DART is driven by binding to both P-cadherin on the tumor cells and CD3 on T cells. Therefore, the concentration of the tri-molecular synapse formed between drug, T cell, and tumor cell, rather than drug concentration, is responsible for efficacy. A mechanistic pharmacokinetic/pharmacodynamic (PK/PD)-driven approach was explored to understand the exposure-response relationship based on the synapse concentration to project the MABEL dose. Orthogonal approaches including PK-driven and receptor occupancy calculations were also investigated. This study showcases the application of PK/PD modeling in immune-oncology, and could potentially be implemented for other bispecific biotherapeutics.

Development of a Target cell-Biologics-Effector cell (TBE) complex-based cell killing model to characterize target cell depletion by T cell redirecting bispecific agents

“…Similarly, the proposed TBE model was able to simultaneously capture the reported in vitro cytotoxicity time course of an extended half-life Dual Affinity Re-Targeting scaffold bispecific directed against CD3 and P-cadherin (P-cadherin LP-DART)-mediated P-cadherin+ HCT116 tumor cell killing by peripheral blood mononuclear cells (PBMCs) at various E:T ratios, 16 suggesting broader applications of the proposed TBE model. Results of the P-cadherin LP-DART modeling are provided in Supplement Materials (Table S1 and Figure S1).…”

“…This simplification was implemented partly because the in vitro cytotoxicity data that were available for model development and validation were all obtained within 96 hours of incubation, and no significant T cell proliferation is expected within 48–96 hours of incubation. 16,55 In addition, an ex vivo cytotoxicity experiment using acute myeloid leukemia patient samples showed that, in patient samples with E:T ratios < 1:10, addition of either anti-programmed cell death 1 (PD-1) or anti- programmed cell death ligand 1 (PD-L1) antibodies significantly augmented AMG 330-induced target cell lysis. In patient samples with E:T ratios > 1:10, the enhancement effect of anti-PD-1 or anti-PD-L1 antibodies on AMG 330-induced target cell lysis was limited, suggesting that the upregulation of PD-1/PD-L1 may be minor at higher E:T ratios (e.g., > 1:10).…”

“…), 3,16,19 the TBE model parameters can usually all be estimated with reasonable confidence. For compounds with insufficient in vitro cytotoxicity data to support development of the entire TBE model, some of the model parameters were fixed to values derived from other similar experiments.…”

“…In vitro cytotoxicity assay data used for model development and evaluation was digitized from the literature; data included: depletion of CD19+ Nalm-6 target cells (150 – 1500 cells per µL) by a human T cell clone (150 – 1500 cells per µL) in the presence of blinatumomab, an anti-CD19xCD3 BiTE, after 4 and 24 hours of incubation; 19 depletion of CD19+ Blin-1 cells (50 cells per µL) by human PBLs (100 – 850 T cells per µL) in the presence of blinatumomab after 4 hours of incubation; 27 depletion of CD19+ Nalm-6 cells (250 cells per µL) by purified human peripheral T cells (625 – 5000 cells per µL) in the presence of blinatumomab after 24 hours of incubation; 23 depletion of CD19+ MEC-1, Nalm-6 and Raji cells (75 – 150 cells per µL) by un-stimulated or pre-stimulated isolated T cells (750 cells per µL) in the presence of blinatumomab after 18 hours of incubation; 48 depletion of P-cadherin+ HCT116 cells (15,000 – 80,000 cells per well, 75 – 400 cells per µL) by PBMCs (15,000 – 400,000 cells per well, 75 – 2000 cells per µL) in the presence of P-cadherin LP-DART after 24 – 96 hours of incubation; 16 depletion of CD33+ OCI-AML3 target cells (22.2 cells per µL) by purified human T cells (22.2 – 222 cells per µL) in the presence of AMG 330, an anti-CD33xCD3 BiTE, after 48 hours of incubation; 3 depletion of FLT3+ REH target cells (100 cells per µL) by activated CD8 + T cells (1000 cells per µL) in the presence of a series of anti-FLT3xCD3 Fabsc bsAbs after 8 hours of incubation; 25 depletion of CD20 + B cells (230 cells per µL) by human T cells (650 cells per µL) in the presence of a series of anti-CD20xCD3 bsAbs after 24 hours of incubation; 26 depletion of Karpas-422, MEC-1, or Raji target cells (150 cells per µL) by PBMCs (1500 cells per µL) in the presence of blinatumomab after 24 hours of incubation 33 . The experimental condition associated parameters were either obtained from literature or leveraged from other studies.…”

“…Recently, three mechanistic PK/PD modeling analyses for bispecific biotherapeutics have been published to guide rational translational research and clinical study design for T-cell redirecting bsAbs. 16–18 All three of these model analyses explored strategies to predict and translate in vivo pharmacodynamic and toxic effects (i.e., cytokine release) using in vitro data for T-cell redirecting bsAbs and physiological system measurements, and accounted for the concentration of the tri-molecular synapse between bsAb, T cell, and target tumor cell. These analyses pioneered the use of mechanism-based PK/PD modeling to characterize the critical steps that govern the pharmacological effects mediated by T-cell redirecting bsAbs.…”