Eli Lilly and Company / Merus N.V.

Solid tumors (CD3-redirecting bispecific T-cell engagers via Merus Biclonics platform)

1.9M US cases/yr · $164.0B Global oncology drug market 2021 (USD MM) · 608570 US cancer deaths annually

Disease Overview

Solid tumors — collectively breast, lung, prostate, colorectal, gastric, pancreatic, ovarian, head & neck, hepatocellular, esophageal and other non-hematologic cancers — represent ~90% of US cancer incidence. The American Cancer Society projected 1.9 million new US cancer cases and 608,570 cancer deaths in 2021, with five-year survival ranging from ~99% (prostate, thyroid, melanoma localized) to <12% (pancreatic, hepatocellular advanced). Standard-of-care therapy depends on indication and biomarker status: cytotoxic chemotherapy, targeted small molecules (EGFR, ALK, BRAF, KRAS G12C, FGFR, HER2 inhibitors), antibody-drug conjugates (Enhertu, Trodelvy, Padcev), monoclonal antibodies (cetuximab, bevacizumab, trastuzumab, rituximab) and immune checkpoint inhibitors (anti-PD-1: pembrolizumab, nivolumab, cemiplimab, dostarlimab, tislelizumab; anti-PD-L1: atezolizumab, durvalumab, avelumab; anti-CTLA-4: ipilimumab; anti-LAG-3: relatlimab). The 2021 global oncology market exceeded $164 billion (IQVIA) and was projected to reach $300+ billion by 2025. CD3-bispecific T-cell engagers — molecules that simultaneously bind a tumor-associated antigen and CD3 on T cells to drive immunological synapse formation and tumor lysis — represented an emerging modality with the only approved precedent at deal date being Amgen's blinatumomab (CD3xCD19 BiTE in B-ALL, approved 2014). The 2021 pipeline contained CD3 bispecifics for hematologic cancers (CD3xBCMA teclistamab, CD3xCD20 mosunetuzumab, glofitamab, epcoritamab, odronextamab) but solid tumor success had eluded the field through gross toxicity, pharmacokinetics and tumor antigen specificity challenges.

Competitive Landscape

At deal date (Jan 2021), the CD3 bispecific T-cell engager landscape was bifurcated between hematologic and solid tumor approaches. Approved/late-stage hematologic CD3 bispecifics included Amgen blinatumomab (CD3xCD19 in B-ALL, approved 2014), Janssen teclistamab (CD3xBCMA in multiple myeloma, BLA filed 2022, approved Oct 2022), Genentech/Roche mosunetuzumab (CD3xCD20 in NHL, approved 2022), Roche glofitamab (CD3xCD20 in DLBCL, approved 2023), Regeneron odronextamab (CD3xCD20), AbbVie/Genmab epcoritamab (CD3xCD20 in DLBCL, approved 2023), Janssen talquetamab (CD3xGPRC5D in MM), Pfizer elranatamab (CD3xBCMA in MM). Solid tumor CD3 bispecifics in development included Roche cibisatamab (CD3xCEA, terminated 2023), Amgen AMG 757 tarlatamab (CD3xDLL3 in SCLC, approved May 2024 as Imdelltra), Amgen AMG 199 (CD3xMUC17 in gastric), Amgen AMG 510 paneltumumab predecessors, Janssen JNJ-78306358 (CD3xHLA-G), Genmab/AbbVie acasunlimab (CD3 + LAG-3), Immunocore tebentafusp (TCR-CD3 bispecific in uveal melanoma, approved Jan 2022), Cytomx CX-904 (CD3xEGFR Probody) and the Merus partnership program. Merus' Biclonics platform — a common-light-chain IgG1 bispecific format — was differentiated by stable, tetravalent IgG-like architecture without heterodimerization defects. Merus' lead independent program at deal date was zenocutuzumab (MCLA-128, HER2xHER3) for NRG1+ tumors, and earlier petosemtamab (MCLA-158, EGFRxLGR5) for head & neck. Loxo Oncology at Lilly entered the deal seeking T-cell engager modality access on the heels of its $8B Loxo acquisition (Jan 2019, Vitrakvi/Retevmo).