Interim results from the pivotal Phase 3 ARTEMIS-008 trial (NCT06498479) show that risvutatug rezetecan, a B7-H3-directed antibody-drug conjugate, significantly reduced the risk of death versus topotecan in patients with relapsed small-cell lung cancer (SCLC) after progression on platinum-based chemotherapy. The findings, presented in a Presidential Symposium session at the 2026 World Conference on Lung Cancer, held September 12 to 15, 2026, in Seoul, South Korea, are the first Phase 3 results showing an overall survival benefit for any Human B7 Homolog 3 (B7-H3)-targeted antibody-drug conjugate (ADC) in any tumor type.
Key Takeaways
- First Positive Phase 3 Data for a B7-H3-Directed Antibody-Drug Conjugate (ADC)
- ARTEMIS-008 met its primary endpoint, with risvutatug rezetecan (HS-20093; GSK5764227) reducing the risk of death by 54% versus topotecan (HR 0.46; 95% CI: 0.35–0.62; p<0.0001) in patients with relapsed small cell lung cancer (SCLC).
- Median overall survival was 18.5 months with risvutatug rezetecan versus 10.3 months with topotecan, with improvements in progression-free survival, objective response rate, and disease control rate.
- Grade 3 or higher treatment-related adverse events occurred less frequently with risvutatug rezetecan (60.9%) than with topotecan (78.2%), with hematologic toxicities predominating.
- Risvutatug rezetecan is one of at least a dozen B7-H3-directed ADCs in clinical development worldwide; the target class has also seen multiple discontinuations across ADC, monoclonal antibody, and bispecific modalities tied to severe toxicities.
- B7-H3 (CD276) is characterized by broad tumor overexpression alongside minimal normal-tissue protein expression, a discordance driven by post-transcriptional regulation; its receptor remains formally unidentified despite two decades of investigation.
- GSK holds exclusive development and commercialization rights to risvutatug rezetecan outside mainland China, Hong Kong, Macau, and Taiwan, with a global registrational program underway across small cell lung cancer and other solid tumors.
An Unmet Need in Relapsed Small Cell Lung Cancer
Small cell lung cancer is a high-grade neuroendocrine malignancy accounting for approximately 10–15% of all lung cancer diagnoses worldwide, with an estimated incidence of 4.7 cases per 100,000 individuals and a five-year overall survival ranging from 12% to 30%.[1] Roughly 70% of patients present with extensive-stage disease, characterized by early metastatic dissemination and a high propensity for relapse following initial chemoimmunotherapy.[2]
Median overall survival for extensive-stage disease treated with current standard-of-care regimens is approximately 12 to 13 months, and outcomes deteriorate substantially after relapse, when few therapies have demonstrated a durable survival benefit.[2] Topotecan remains among the most widely used agents in the relapsed setting, but is associated with modest response rates and substantial hematologic toxicity, underscoring the longstanding need for treatments capable of extending survival with a more favorable safety profile in this population, as well as in other solid tumors where similarly limited later-line options persist.
B7-H3 as a Therapeutic Target
Human B7 Homolog 3 (B7-H3), also known as CD276, is a transmembrane immune checkpoint protein belonging to the B7 family. In humans, it exists as two isoforms, 2IgB7-H3 and 4IgB7-H3, arising from partial domain duplication; the 4Ig form predominates in most normal tissues and tumor cell lines, while the 2Ig form appears more tumor-restricted in certain malignancies, including glioma and acute myeloid leukemia.[3]
A defining and therapeutically relevant feature of B7-H3 biology is the marked discordance between its broad messenger RNA expression across normal tissues and its minimal protein expression in the same tissues, a gap attributed to post-transcriptional regulation by microRNAs of the miR-29 family. In tumors, this regulatory constraint is lost, resulting in marked protein overexpression across more than ten solid tumor types, including small cell and non-small cell lung cancer, prostate cancer, osteosarcoma, and various sarcomas, while normal-tissue protein expression remains low.[3]
The differential expression pattern has positioned B7-H3 as an attractive antigen for antibody-drug conjugate targeting, offering the potential for tumor-selective cytotoxic payload delivery with limited on-target, off-tumor exposure, although expression is frequently heterogeneous both between and within tumors.
Despite more than two decades of study, researchers have not identified a definitive receptor for B7-H3; proposed binding partners, including TLT-2, IL-20RA, PLA2R1, and AAMP, each has experimental support but remains unvalidated or controversial.[3] In the absence of a confirmed receptor, B7-H3’s immunomodulatory activity is understood primarily through function: it suppresses CD4-positive and CD8-positive T-cell proliferation and interferon-gamma production, inhibits natural killer cell cytotoxicity, and promotes M2-like macrophage polarization within the tumor microenvironment, collectively contributing to immune evasion.[3]
Independent of these immune effects, B7-H3 also drives tumor progression through non-immune mechanisms, including activation of the JAK2/STAT3, PI3K/AKT/mTOR, and NF-κB signaling pathways, which support proliferation, glycolytic metabolism, angiogenesis, and chemoresistance.[3] High B7-H3 expression is consistently associated with adverse clinical outcomes across a broad range of tumor types, reinforcing its relevance as both a therapeutic target and a prognostic biomarker.
ARTEMIS-008 Trial Design and Results
ARTEMIS-008 (NCT06498479) is a multicenter, randomized, open-label, active-controlled Phase 3 trial conducted in China by Hansoh Pharmaceutical Group Co., Ltd., evaluating risvutatug rezetecan against topotecan in patients with limited- or extensive-stage SCLC whose disease had progressed on or after first-line platinum-based therapy. A total of 461 patients were randomized 1:1 to receive risvutatug rezetecan at 8.0 mg/kg intravenously every three weeks or topotecan at 1.2 mg/m² on days 1 through 5 of each 21-day cycle. The primary endpoint was overall survival, with progression-free survival, objective response rate, disease control rate, duration of response, and safety as secondary endpoints.
At a median follow-up of 12.2 months, risvutatug rezetecan met the primary endpoint, reducing the risk of death by 54% relative to topotecan (HR 0.46; 95% CI: 0.35–0.62; p<0.0001). Median overall survival was 18.5 months with risvutatug rezetecan compared with 10.3 months with topotecan, and 12-month overall survival rates were 64.5% versus 43.3%, respectively. The survival benefit was consistent across prespecified subgroups.
Secondary efficacy endpoints, assessed by an independent review committee, likewise favored risvutatug rezetecan. Median progression-free survival was 7.2 months versus 3.0 months (HR 0.33; 95% CI: 0.25–0.42), objective response rate was 58.3% versus 12.6%, and disease control rate was 90.4% versus 60.2% for risvutatug rezetecan and topotecan, respectively.
The safety profile favored risvutatug rezetecan based on severe treatment-related adverse events, which occurred in 60.9% of patients receiving risvutatug rezetecan compared with 78.2% of those receiving topotecan. The most common grade 3 or higher treatment-related adverse events with risvutatug rezetecan were hematologic, including decreased neutrophil, white blood cell, lymphocyte, and platelet counts, along with anemia, findings considered consistent with the known toxicity profile of this ADC class.
Mechanism and Development Program
Risvutatug rezetecan (HS-20093, GSK5764227) is a B7-H3-directed antibody-drug conjugate discovered by Hansoh Pharmaceutical, comprising a fully human anti-B7-H3 monoclonal antibody conjugated to rezetecan, an exatecan-derived topoisomerase I inhibitor payload, via a tetrapeptide-based cleavable linker. Notably, rezetecan is not unique to this molecule. The same payload class underlies several other ACDs originating from Chinese biopharmaceutical developers directed against unrelated targets, including the HER2-directed trastuzumab rezetecan (SHR-A1811, Jiangsu Hengrui Pharmaceuticals) and the B7-H4-directed mocertatug rezetecan (GSK5733584, also GSK-partnered), illustrating a broader industry pattern of sharing validated topoisomerase I inhibitor chemistry across differentiated antibody scaffolds and tumor targets.
Foundational Phase Ia/Ib data from the ARTEMIS-001 trial (NCT05276609), conducted in 306 patients with previously treated advanced solid tumors, established a maximum tolerated dose of 12.0 mg/kg and confirmed antitumor activity in lung cancer, with confirmed objective response rates in the range of 50–54% among SCLC patients across the 8.0 and 10.0 mg/kg dose levels.[4] Among 236 lung cancer patients treated at these two dose levels, treatment-related interstitial lung disease occurred in 3.4% of patients and adverse events leading to death occurred in 3.8%, findings consistent with the known toxicity profile of topoisomerase I inhibitor-based antibody-drug conjugates and considered by investigators in dose selection for pivotal testing.[4] A separate Phase I cohort in NSCLC reported a confirmed objective response rate of 33.3% among patients with non-squamous disease without actionable genomic alterations at the 8.0 mg/kg dose, supporting continued evaluation of risvutatug rezetecan beyond SCLC.
Under a December 2023 license agreement, GSK holds exclusive rights to develop and commercialize risvutatug rezetecan outside mainland China, Hong Kong, Macau, and Taiwan, while Hansoh Pharmaceutical retains rights within these territories and plans to pursue a regulatory submission in China based on the ARTEMIS-008 data.
GSK’s global development program, EMBOLD, has enrolled more than 1,000 patients to date and includes the Phase 3 EMBOLD SCLC-301 trial (NCT07099898) evaluating risvutatug rezetecan in relapsed extensive-stage SCLC outside China, with pivotal data anticipated in 2027, along with planned Phase 3 studies in earlier-line SCLC and metastatic prostate cancer. The molecule has received several expedited regulatory designations, including Breakthrough Therapy Designation from the US FDA for relapsed or refractory extensive-stage SCLC and for late-line relapsed or refractory osteosarcoma, Orphan Drug Designation in the US, Japan, and the European Union for SCLC, and Priority Medicines (PRIME) designation from the European Medicines Agency (EMA) for relapsed extensive-stage SCLC.[5][6][7][8][9]
B7-H3-Directed ADCs – A Competitive Landscape
Risvutatug rezetecan enters a competitive field of B7-H3-targeted therapeutics, several of which illustrate both the promise and the toxicity challenges associated with this target.
Ifinatamab deruxtecan (I-DXd; DS-7300A), developed by Daiichi Sankyo using its DXd ADC platform and jointly advanced with Merck, is the most clinically advanced rival program. Comprising a humanized anti-B7-H3 monoclonal antibody conjugated to an exatecan-derived topoisomerase I inhibitor via a tetrapeptide-based cleavable linker, ifinatamab deruxtecan has reported an objective response rate of approximately 48–55% and a median overall survival of approximately 10–12 months in pretreated extensive-stage SCLC across its Phase 1/2 and Phase 2 IDeate-Lung01 (NCT05280470) programs.[10][11]
The FDA accepted a biologics license application for ifinatamab deruxtecan in this setting in 2026 under priority review, following Breakthrough Therapy Designation granted in 2025. The agent has also been associated with interstitial lung disease, a toxicity recognized across DXd-based antibody-drug conjugates.
A broader field of earlier-stage B7-H3-directed antibody-drug conjugates has also emerged from Chinese biopharmaceutical developers, several with encouraging early efficacy signals in SCLC and other solid tumors. YL201*, conjugated to a topoisomerase I inhibitor payload, has reported disease control rates above 80% and objective response rates of approximately 64% in extensive-stage SCLC and 49% in nasopharyngeal carcinoma in early-phase testing.
DB-1311 (BNT324), developed by DualityBio in collaboration with BioNTech, and MHB088C have each reported encouraging response and disease control rates in heavily pretreated SCLC and prostate cancer cohorts, while 7MW3711 (Mabwell) has reported an objective response rate exceeding 60% in a small SCLC cohort. AbbVie’s mirzotamab clezutoclax (ABBV-155), which conjugates a B7-H3-targeted antibody to a BCL-XL inhibitor payload rather than a topoisomerase inhibitor, has reported more modest response rates in SCLC, NSCLC, and breast cancer cohorts to date. MacroGenics’ MGC026, a newer SYNtecan E**-based B7-H3 antibody-drug conjugate, remains in early clinical evaluation (NCT06242470).[13]
Beyond conventional ADCs, NanoValent Pharmaceuticals is developing B7-H3-directed candidates on a distinct, preclinical-stage nanoparticle platform, including NV104 (irinotecan; anti-B7-H3) and NV106 (temozolomide; anti-B7-H3), built on the company’s Hybrid Polymerized Liposomal Nanoparticle (HPLN) technology as targeted nano-ADC (nADC/TNS). According to the company, validation programs for NV104 and NV106 in glioblastoma and other B7-H3 (CD276)-expressing tumors are planned but have not yet entered clinical testing.[14]
Other B7-H3-directed programs have encountered more substantial setbacks. Vobramitamab duocarmazine (MGC018), a MacroGenics antibody-drug conjugate pairing a B7-H3-targeted antibody with a DNA-alkylating duocarmycin payload, was discontinued for company-sponsored development following a 2024 review of Phase II data in metastatic castration-resistant prostate cancer, after an independent safety monitoring committee recommended halting treatment for safety reasons.[12][13]
Earlier B7-H3-directed approaches using non-ADC modalities have also faced challenges: the monoclonal antibody enoblituzumab (MGA271) was halted after drug-related mortality in a Phase 2 head and neck cancer trial, and the CD3/B7-H3 bispecific DART molecule MGD009 was terminated in a Phase 1 trial due to hepatotoxicity.[13]
B7-H3 is also being pursued through modalities beyond antibody-drug conjugates, with CAR T-cell approaches offering an instructive parallel on the target’s broader validation and its recurring challenges. A preclinical study from St. Jude Children’s Research Hospital, published in August 2026, reported that deletion of the inhibitory ribonuclease Regnase-1 in B7-H3-directed CAR T cells improved tumor control and prevented pulmonary metastasis in mouse models of osteosarcoma, an indication in which risvutatug rezetecan has separately received Breakthrough Therapy Designation, with the engineered cells advancing toward an early-phase clinical trial.[15] This work illustrates the cross-modality interest in B7-H3 as a tumor-restricted antigen, while underscoring that antigen selection alone has not been sufficient to guarantee clinical translation across the therapeutic classes directed against it.
Collectively, this experience underscores that despite B7-H3’s favorable differential expression between tumor and normal tissue, clinical translation across this target class has been uneven, with efficacy signals in SCLC, prostate cancer, and gynecologic malignancies tempered by recurring hematologic and, in select programs, more severe safety findings. The overall survival benefit demonstrated in ARTEMIS-008 represents a notable data point in this context, as the first randomized Phase III confirmation that a B7-H3-directed antibody-drug conjugate can extend survival in a molecularly defined solid tumor population.
Note
* YL201 is being developed by MediLink Therapeutics, which partnered with Roche for its global development and commercialization outside of mainland China, Hong Kong, and Macau;
** SYNtecan E™ is a linker-payload technology developed by Lonza. Further detail on risvutatug rezetecan and other B7-H3-directed antibody-drug conjugates in development is available through the ADC Drug Map.
Clinical Trials
ARTEMIS-008HS-20093 Compared With Topotecan in Subjects With Relapsed Small Cell Lung Cancer – ClinicalTrials.gov ID NCT06498479
ARTEMIS-001: Phase 1 Study of HS-20093 in Patients With Advanced Solid Tumors – ClinicalTrials.gov ID NCT05276609
A Study of GSK5764227 in Participants With Relapsed Small Cell Lung Cancer (SCLC) – ClinicalTrials.gov ID NCT07099898
Ifinatamab Deruxtecan (I-DXd) in Subjects With Pretreated Extensive-Stage Small Cell Lung Cancer (ES-SCLC) (IDeate-Lung01) – ClinicalTrials.gov ID NCT05280470
A Study of MGC026 in Participants With Advanced Solid Tumors – ClinicalTrials.gov ID NCT06242470
References
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[12] MacroGenics, Inc. Form 10-K, Fiscal Year 2025. US Securities and Exchange Commission.
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Featured image: Seoul, 大韓民国. Photo courtesy: © 2020. Used with permission under the Unsplash License.
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