Phase 1, first-in-human study of TYRP1-TCB (RO7293583), a novel TYRP1-targeting CD3 T-cell engager, in metastatic melanoma: active drug monitoring to assess the impact of immune response on drug exposure

Abstract

Introduction: Although checkpoint inhibitors (CPIs) have improved outcomes for patients with metastatic melanoma, those progressing on CPIs have limited therapeutic options. To address this unmet need and overcome CPI resistance mechanisms, novel immunotherapies, such as T-cell engaging agents, are being developed. The use of these agents has sometimes been limited by the immune response mounted against them in the form of anti-drug antibodies (ADAs), which is challenging to predict preclinically and can lead to neutralization of the drug and loss of efficacy.

Methods: TYRP1-TCB (RO7293583; RG6232) is a T-cell engaging bispecific (TCB) antibody that targets tyrosinase-related protein 1 (TYRP1), which is expressed in many melanomas, thereby directing T cells to kill TYRP1-expressing tumor cells. Preclinical studies show TYRP1-TCB to have potent anti-tumor activity. This first-in-human (FIH) phase 1 dose-escalation study characterized the safety, tolerability, maximum tolerated dose/optimal biological dose, and pharmacokinetics (PK) of TYRP1-TCB in patients with metastatic melanoma (NCT04551352).

Results: Twenty participants with cutaneous, uveal, or mucosal TYRP1-positive melanoma received TYRP1-TCB in escalating doses (0.045 to 0.4 mg). All participants experienced ≥1 treatment-related adverse event (TRAE); two participants experienced grade 3 TRAEs. The most common toxicities were grade 1-2 cytokine release syndrome (CRS) and rash. Fractionated dosing mitigated CRS and was associated with lower levels of interleukin-6 and tumor necrosis factor-alpha. Measurement of active drug (dual TYPR1- and CD3-binding) PK rapidly identified loss of active drug exposure in all participants treated with 0.4 mg in a flat dosing schedule for ≥3 cycles. Loss of exposure was associated with development of ADAs towards both the TYRP1 and CD3 domains. A total drug PK assay, measuring free and ADA-bound forms, demonstrated that TYRP1-TCB-ADA immune complexes were present in participant samples, but showed no drug activity in vitro.

Discussion: This study provides important insights into how the use of active drug PK assays, coupled with mechanistic follow-up, can inform and enable ongoing benefit/risk assessment for individuals participating in FIH dose-escalation trials. Translational studies that lead to a better understanding of the underlying biology of cognate T- and B-cell interactions, ultimately resulting in ADA development to novel biotherapeutics, are needed.

Keywords: ADA; TCB; TYRP1; anti-drug antibody; antibody; bispecific; immunogenicity; metastatic melanoma.

Figure 1

Temporal profile of cytokines. Profile of selected cytokines in the first three cycles of TYRP1-TCB treatment. IFN-γ and CXCL10 increases in all cohorts whereas IL-6 (and TNF-α) levels are maintained over time in the fractionated dosing cohort. C, cycle; CXCL10, C-X-C motif chemokine ligand 10; D, day; EOI, end of infusion; h, hours; IFN-γ, interferon-gamma; IL-6, interleukin-6; TCB, T-cell engaging bispecific; TNF-α, tumor necrosis factor-alpha; TYRP1, tyrosinase-related protein 1.

Figure 2

Cytokine profile according to CRS. Cytokine profiles according to presence (red) or absence (black) of CRS. Patients who developed CRS displayed an elevated induction of CXCL10, IFN-γ, IL-6 and TNF-α upon first dosing with 0.4 mg TYRP1-TCB. C, cycle; CRS, cytokine release syndrome; CXCL10, C-X-C motif chemokine ligand 10; D, day; EOI, end of infusion; h, hours; IFN-γ, interferon-gamma; IL-6, interleukin-6; TNF-α, tumor necrosis factor-alpha.

Figure 3

Immunogenicity and effect on exposure. (A) First-dose PK of TYRP1-TCB following intravenous infusion of 0.05, 0.1, and 0.4 mg TYRP1-TCB (Participants #3–20). (B) Example PK profile following fractionated dosing of 0.05 mg, 0.1 mg (7 days later), 0.4 mg (21 and 42 days later) TYRP1-TCB (Participant #16). (C) Example (Participant #7) of the effect of ADA onset (red) on TYRP1-TCB PK (blue). (D) Loss of exposure (assessed using EOI concentration data) across all 8 participants administered with 0.4 mg TYRP1-TCB (flat dosing) shows generality of ADA effect exemplified in element (C). BLQ values set as 1 ng/mL for illustrative purposes in this figure. Participant #9 (data shown in hollow orange circles) exhibited a weaker ADA response resulting in only partial loss of active TYRP1 TCB; data from all other participants are shown using solid blue circles. (E) Y values: C_max (each administration, EOI measurement) plotted as a percentage of dose-normalized first administration C_max (Cycle 1 Day 1); X values: ADA titer for all ADA-positive participants (Participants #3, #4, #6–9, #13, #19). Participant #9 (data shown in hollow orange circles) exhibited a weaker ADA response resulting in only partial loss of active TYRP1 TCB; data from all other participants are shown using solid black circles. (F) Domain detection assay using ADA-positive sera from Participant #3 shows ADAs react to both TYRP1 and CD3 domains of the TYRP1-TCB. All other examined participants also showed ADAs targeting both the TYRP1 and CD3 domains. Y-scales: signal/noise ratios for the different assays, arbitrary units. ADA, anti-drug antibody; BLQ, below the limit of quantification; C_max, maximum (peak) serum concentration; d, days; EOI, end of infusion; PK, pharmacokinetic; s/n, signal-to-noise ratio; TCB, T-cell engaging bispecific; TYRP1, tyrosinase-related protein 1.

Figure 4

Comparison of total and active drug exposure for selected participants and in vitro activity of ADA-positive and ADA-negative participant sera. Comparison of total and active drug concentration in participants who developed ADAs: (A) Schematic of key elements of active and total drug assay methods. (B) Example of moderate ADA impact in Cycle 3 for Participant #6 (titer of 300 in Cycle 3 predose sample). (C) Example of high ADA impact in Cycle 3 for Participant #7 (titer of 2700 in Cycle 3 predose sample). (D) Schematic of in vitro activity assay. (E) and (F) Activity of participant sera before (C1 EOI) and after (C4 EOI) onset of ADA response performed in two separate experiments. Created with BioRender.com. ADA, anti-drug antibody; C, cycle; cAMP, cyclic adenosine monophosphate; CHO, Chinese hamster ovary; D, day; EOI, end of infusion; NFAT(-RE), nuclear factor of activated T cells (-reporter); RLU, relative light unit; TCR, T-cell receptor; TYRP1, tyrosinase-related protein 1.