DS-9606 is a Claudin 6 (CLDN6)-targeting antibody-drug conjugate (ADC) utilizing Daiichi Sankyo's proprietary mPBD payload. This anticancer agent forms covalent crosslinks in the minor groove of tumor cell DNA, blocking cell division and inducing cell death. Daiichi Sankyo had planned multiple ADCs employing the mPBD platform, with DS-9606 intended as the first clinical candidate in this series.

Regarding the termination of DS-9606's development, Daiichi Sankyo's R&D head clarified during an earnings call that this decision does not reflect a failure of the technological platform. The company has confirmed the drug's potential, as its Phase I trial demonstrated preliminary clinical activity and a favorable safety profile in solid tumors like germ cell tumors.

"The field remains promising for further development, but based on an overall portfolio assessment, we decided not to pursue internal R&D in this area independently." It is reported that CLDN6 primarily targets rare tumors such as germ cell tumors, with a global annual incidence of fewer than 100,000 cases.

Coinciding with this news, Daiichi Sankyo released its financial results for the first three quarters of fiscal year 2025 (April 2025 – March 2026). The data shows a 12.1% year-over-year increase in revenue to ¥15.3 trillion (approximately $102 billion), with core operating profit reaching ¥249.2 billion, up 8.8% year-over-year.

The core drivers of this performance were the two ADCs, Enhertu and Datroway, which together contributed ¥538.4 billion (approximately $3.442 billion) in revenue, accounting for 35.1% of total revenue. This solidifies Daiichi Sankyo's position as the pharmaceutical company with the highest proportion of revenue derived from ADC business globally.

Enhertu continued its strong performance, with quarterly sales reaching ¥188.0 billion and cumulative sales for the first three quarters totaling ¥506.8 billion (approximately $3.398 billion), a 25.3% year-over-year increase. On a calendar year basis, Enhertu's global sales for 2025 reached ¥655.2 billion (approximately $4.373 billion), a 24.97% increase from the previous year. Benefiting from penetration in HER2-positive breast cancer, gastric cancer, and other indications, the therapy is now available in over 90 countries and regions.

Datroway, the TROP2-targeting ADC launched in December 2024, generated cumulative sales of ¥31.6 billion (approximately $212 million) for the first three quarters, with single-quarter sales of ¥14.5 billion, representing a 52.9% sequential growth. It is still in the early stages of commercialization.

Despite being developed on Daiichi Sankyo's DXd ADC platform, Datroway's path to approval has been rocky. In 2024, its marketing application was withdrawn by Daiichi Sankyo and partner AstraZeneca after it failed to demonstrate a statistically significant improvement in overall survival for patients with previously treated non-squamous non-small cell lung cancer (NSCLC).

Furthermore, the data readout for another key Phase III trial of Datroway (the AVANZAR study) has been delayed again. This study evaluates Datroway in combination with AstraZeneca's Imfinzi as a first-line treatment for NSCLC. The data release, initially planned for the second half of 2025, was first postponed to the first half of 2026 and is now expected in the second half of 2026. The official explanation cites a "slower-than-expected rate of clinical event occurrence" as the primary reason.

However, on February 3rd, Daiichi Sankyo and AstraZeneca announced that the U.S. FDA has accepted the supplemental Biologics License Application (sBLA) for Datroway and granted it Priority Review. The application seeks approval for treating adult patients with unresectable or metastatic triple-negative breast cancer (TNBC) who are not candidates for PD-1/PD-L1 inhibitor therapy. The FDA is expected to make a regulatory decision in the second quarter of 2026.

Daiichi Sankyo aims to expand its ADC portfolio by 2030, targeting at least four ADC products across multiple indications to reach approximately 700,000 patients globally—a nearly sixfold increase from the 120,000 patients in 2025. Financial reports show that Daiichi Sankyo's R&D investment for the first three quarters was ¥338.7 billion, a 12.7% year-over-year increase.

To date, among the six ADCs in development based on the DXd platform, two are marketed (Enhertu, Datroway), two are in Phase III trials (I-DXd, R-DXd), and the remaining two (DS-3939, DS-3610) are in early-stage clinical development.

Previously, the HER3-targeting ADC, patritumab deruxtecan, faced a significant setback for the platform when its marketing application was withdrawn in the spring of 2025 after failing to meet the prespecified threshold for statistical significance in overall survival in a Phase III trial.

While Daiichi Sankyo adjusts its pace, multinational pharmaceutical giants are accelerating their positioning in the ADC arena.

At this year's JPM Conference, ADCs were highlighted alongside GLP-1 drugs as the dual core growth engines in oncology for leading global pharmaceutical companies (MNCs). Most Top 10 pharma giants, including AstraZeneca, Merck & Co. (MSD), Pfizer, Roche, and Bristol Myers Squibb (BMS), have elevated ADC development to an unprecedented strategic priority.

According to a research report released by Orient Securities in January 2026, global R&D investment in the ADC field by MNCs is accelerating. During the 2025-2026 period, the total R&D and business development (BD) investment in ADCs by the Top 5 pharma companies alone is projected to exceed $20 billion, representing an increase of approximately 40% compared to 2023-2024. This funding is primarily allocated to pipeline expansion, combination therapy development, and the licensing of innovative Chinese assets.

Merck & Co.'s strategy is highly representative. In 2023, it secured collaboration rights to several Daiichi Sankyo ADCs for $5.5 billion. Earlier, it spent nearly $1.4 billion to license the TROP2-targeting ADC, SKB264/MK-2870 (Sacituzumab tirumotecan), from Kelun-Biotech, placing it at the core of its oncology strategy.

As of January 2026, Merck has initiated over ten Phase III clinical trials for SKB264, nine of which are in combination with its blockbuster PD-1 inhibitor, Keytruda (pembrolizumab). These studies cover lung cancer, breast cancer, endometrial cancer, and other tumor types, making Merck one of the most active players in the field of Immuno-Oncology (IO) + ADC combination therapies.

Notably, the combination of SKB264 and pembrolizumab for the first-line treatment of PD-L1 positive non-small cell lung cancer (NSCLC) has met the primary endpoint in a Phase III trial, showing significant improvement in progression-free survival (PFS) and a positive trend in overall survival (OS). This regimen has received Breakthrough Therapy Designation from China's NMPA.

Public data shows that in 2025, combination therapies accounted for approximately 58% of newly initiated global ADC clinical trials. Among these, IO+ADC combinations (ADC + PD-1/PD-L1 inhibitor) constituted 68% of all combination therapies, making it the most popular combination strategy. Industry analysis suggests that this pairing achieves a synergistic effect of "targeted killing + immune activation," and combination regimens are expected to capture about half of the ADC market in the next 3-5 years.

Pfizer's ADC strategy is also tightly focused on IO+ADC combinations. Its Nectin-4 targeting ADC, Padcev (enfortumab vedotin), developed with Astellas, in combination with Keytruda is already approved for urothelial carcinoma. Efforts are now underway to expand this combination into new indications. Pfizer's key investigational ADC, Sigvotatug Vedotin, targets ITGB6 and is being studied both as a monotherapy and in combination with Keytruda for NSCLC.

Furthermore, Pfizer plans to initiate Phase III trials in 2026 to evaluate combinations of its in-licensed PD-1/VEGF bispecific antibody, PF-08634404, with Padcev and other internal ADCs, further solidifying its IO+ADC strategy.

Simultaneously, a force from the East is rapidly transforming from a "new force" into a "main force."

2025 was a record year for Chinese ADCs in terms of out-licensing deals, clinical trials, and approved new drugs. According to Southwest Securities data, overseas licensing deals for Chinese ADC drugs in 2025 generated a total upfront payment of $1.63 billion, a staggering 676.2% year-over-year increase. The total deal value reached $21.13 billion, a 390.6% increase (including a landmark portfolio deal from Innovent Biologics in October).

These deals covered both established targets like HER2 and TROP2, as well as emerging targets like CDH6 and ROR1. For example, in February 2025, CStone Pharmaceuticals' subsidiary, Jupiter Bioscience, out-licensed its ROR1 ADC, SYS6005, to Radiance Biopharma in a deal worth over $1.2 billion, making it the first ROR1 ADC from China to be licensed overseas.

The quality of Chinese ADC innovation continues to rise. The Antibodies to watch in 2026 report indicated that of the 19 novel antibody drugs first approved globally in 2025, 10 received their first approval in China, including 3 ADCs. The R&D cost for domestically developed novel antibody drugs in China is estimated to be only 20%-30% of that in the U.S., and the clinical development cycle is typically 1-2 years shorter than in Europe and the U.S., highlighting significant efficiency advantages.

As one innovative drug investor noted, ADCs represent a key breakthrough for Chinese pharmaceutical companies to compete globally, with cost and efficiency advantages serving as the core foundation.

As an increasing number of players enter the field, the ADC industry is transitioning from an early phase of technological exploration and capital enthusiasm into a new stage where data and clinical differentiation determine success. The industry consensus is that mere technological narratives are no longer sufficient—genuine "clinical value" has become the sole passport to advancement.

In 2025, ADC drugs globally accelerated their expansion from later-line treatments into first-line and early-stage therapies. Breakthroughs were achieved in applications for several key indications, including sacituzumab govitecan for first-line treatment of triple-negative breast cancer (TNBC) and trastuzumab deruxtecan for adjuvant treatment of HER2-positive early breast cancer. These milestones lay the groundwork for subsequent indications and drive ADCs toward comprehensive coverage across the entire treatment cycle.

From Daiichi Sankyo's pipeline adjustments, to accelerated deployments by pharmaceutical giants, to breakthroughs by Chinese biopharma companies—competition in the ADC arena has intensified. Looking ahead, as combination therapies become widespread and emerging targets achieve breakthroughs, the story of ADC as the "magic bullet" will continue to unfold.