Merck & Co. Inc. / Kelun-Biotech Biopharmaceuticals Co. Ltd.

Solid Tumors (ADC Platform)

1.9M US cases/yr · $9.7B Global Market · 36% YoY ADC Market Growth (2023)

Disease Overview

Antibody-drug conjugates combine targeted monoclonal antibodies with cytotoxic payloads via chemical linkers, delivering chemotherapy directly to cancer cells while sparing healthy tissue. The ADC class has experienced explosive growth driven by approvals of Enhertu, Padcev, and other next-generation agents across multiple solid tumor types.

Competitive Landscape

At deal time, Daiichi Sankyo/AstraZeneca's Enhertu was the dominant ADC franchise with $4B+ revenue. Merck's $9.3B Kelun deal secured seven preclinical ADC candidates to build a diversified ADC pipeline, complementing its separate $5.5B Daiichi Sankyo ADC partnership announced later in 2023.

Solid Tumors

1.6M US cases/yr · $95.0B US Solid Tumor Oncology Market

Disease Overview

Merck licensed an undisclosed ADC candidate from Kelun-Biotech for solid tumor treatment, the second of three ADC deals between the companies in 2022. Kelun-Biotech received $35M upfront with up to $901M in milestones. The first deal included SKB-264 (TROP2 ADC), demonstrating Merck strategic commitment to building a broad ADC portfolio to complement Keytruda.

ADC Strategic Context

Merck pursued an aggressive ADC licensing strategy in 2022, signing three separate deals with Kelun-Biotech totaling $9.3B in potential payments. This reflected the industry ADC renaissance driven by Enhertu success. Merck ADC strategy aims to develop combination approaches with Keytruda to extend its immuno-oncology franchise beyond PD-1 checkpoint blockade.

Solid Tumors (Undisclosed ADC Target)

500K US cases/yr · $15.0B Global ADC oncology market 2022 · ~15 ADCs approved globally by end-2022

Disease Overview

Merck's second 2022 ADC license from Kelun-Biotech targets undisclosed solid tumor antigens, slotting into a platform strategy that expanded across 2022-2023 into a nine-program partnership. The addressable solid-tumor population spans validated ADC targets including TROP2 (NSCLC ~236,000 U.S. annual cases; HR+/HER2- breast ~200,000 U.S. annual cases; TNBC ~40,000 U.S. annual cases), HER2-low/ultra-low breast cancer (expanded target population post-DESTINY-Breast04), CLDN18.2 in gastric/pancreatic (~27,000 and ~64,000 U.S. annual cases respectively), and emerging antigens across lung, ovarian, and GI malignancies. Merck's public strategic narrative frames ADCs as the central pillar of its post-Keytruda (2028-2029 LOE) oncology franchise, with TROP2 ADC SKB264/MK-2870 positioned for multi-indication Phase 3 readouts 2024-2026. The second Kelun transaction specifically covers a preclinical ADC with Pre-IND status at the time of the July 2022 signing, and low upfront ($35M cash) reflects early-stage risk profile versus the ~$10B+ downstream potential Merck has since committed across all three Kelun deals combined.

Competitive Landscape

The ADC competitive landscape at the time of the July 2022 second Kelun deal was dominated by Enhertu (trastuzumab deruxtecan, Daiichi Sankyo/AstraZeneca) with landmark DESTINY-Breast04 HER2-low data that had just read out in June 2022, Trodelvy (sacituzumab govitecan, Gilead) in TNBC and urothelial, Padcev (enfortumab vedotin, Seagen/Astellas) anchoring urothelial cancer, Adcetris (brentuximab vedotin, Seagen/Takeda) in classical Hodgkin lymphoma, Kadcyla (trastuzumab emtansine, Roche) in HER2+ breast, and Polivy (polatuzumab vedotin, Roche) in DLBCL. Emerging modality competitors included Elahere (mirvetuximab soravtansine, ImmunoGen, subsequently AbbVie) approved November 2022 in FRα+ ovarian. Merck's cumulative Kelun stack — SKB264 (TROP2 ADC), this second undisclosed asset, and the seven-asset January 2023 platform follow-on — builds a multi-program ADC arsenal to rival AstraZeneca/Daiichi's ADC alliance in breadth as Keytruda faces LOE.

Advanced Breast Cancer

Competitive Landscape

Advanced/metastatic breast cancer ADC competition is stratified by target antigen. TROP2-directed ADCs (direct competitor class for Kelun's sac-TMT/MK-2870): Trodelvy (sacituzumab govitecan, Gilead) is approved in HR+/HER2- and mTNBC, generating ~$1.3B in 2024 net product revenue per Gilead 10-K. Datroway (datopotamab deruxtecan, Daiichi Sankyo/AstraZeneca) received FDA accelerated approval in January 2025 for previously treated HR+/HER2- metastatic breast cancer based on TROPION-Breast01. HER2-directed ADCs: Enhertu (trastuzumab deruxtecan, Daiichi/AstraZeneca) dominates HER2+ and HER2-low segments with Daiichi reporting ~$3.7B global 2024 sales and is increasingly the second-line standard; Kadcyla (ado-trastuzumab emtansine, Roche) retains residual post-neoadjuvant use. HER3-directed ADCs: patritumab deruxtecan (Daiichi/Merck) received a 2024 CRL and is re-running pivotal trials. Commercial threat assessment for MK-2870: Kelun's asset enters a crowded TROP2 field where Trodelvy owns mTNBC mindshare, Dato-DXd secures HR+/HER2- after CDK4/6 failure, and Enhertu's HER2-low expansion has compressed the ADC-naive patient pool. Merck's wedge is Keytruda-combination leverage and potential earlier-line positioning; pricing and cross-payload resistance will define share.