Ris-Rez ARTEMIS-008 OS Win: China-Only Data Obscures Global Ambition for First B7-H3 ADC

Hansoh Pharma's Ris-Rez Achieves Phase III Success in SCLC

GSK's partner, Hansoh Pharmaceutical, announced positive Phase III results for its antibody-drug conjugate (ADC), risvutatug rezetecan (Ris-Rez), in patients with advanced or relapsed small-cell lung cancer (SCLC) in China. The ARTEMIS-008 trial (NCT06498479) met its primary endpoint of overall survival (OS), demonstrating statistically significant and clinically meaningful improvements compared to standard-of-care topotecan. Consistent benefits were also observed in key secondary endpoints like progression-free survival (PFS), with a safety profile consistent with prior findings. This marks the first positive Phase III OS data for a B7-H3-targeted ADC in any tumor type.

• The pivotal ARTEMIS-008 Phase III trial for risvutatug rezetecan in advanced or relapsed SCLC patients in China successfully met its primary endpoint of overall survival (OS). The drug showed statistically significant and clinically meaningful improvements in OS compared to topotecan, the standard of care, alongside consistent benefits in secondary endpoints such as progression-free survival (PFS).
• These results represent the first positive Phase III overall survival data reported for a B7-H3-targeted ADC across any tumor type, validating B7-H3 as a promising target in lung cancer and other solid tumors. The safety profile of Ris-Rez was consistent with previous findings, with no new safety signals identified, supporting its potential for patients with extensive stage SCLC who face a poor prognosis.
• Hansoh Pharma will use these positive data for regulatory submission in China. GSK, which holds exclusive development and commercialization rights for Ris-Rez worldwide (excluding Greater China) through a deal worth up to $1.71 billion, is advancing a broad global clinical development program, including the Phase III EMBOLD SCLC-301 trial. Ris-Rez has also received multiple regulatory designations, including Orphan Drug, PRIME, and Breakthrough Therapy.

ARTEMIS-008: Risvutatug Rezetecan Shows Significant OS Benefit in SCLC

Several recent studies have advanced the understanding of treatment approaches across lines of therapy in extensive-stage and relapsed SCLC. The EORTC 1417 REACTION trial, a multicenter, open-label, randomized phase II study, evaluated the addition of pembrolizumab to platinum-etoposide followed by pembrolizumab maintenance versus platinum-etoposide alone in 119 chemo-sensitive extensive-disease SCLC patients who responded after two induction cycles. Despite a numerically favorable OS trend (12.3 vs. 10.4 months; HR 0.73, 1-sided p=0.097), the primary endpoint of PFS was not met (4.7 vs. 5.4 months; HR 0.84, 1-sided p=0.194), and grade ≥3 adverse events were more frequent in the pembrolizumab arm (37% vs. 26%). The RATIONALE-312 phase III trial (NCT04005716) randomized 457 ES-SCLC patients 1:1 to tislelizumab plus chemotherapy or placebo plus chemotherapy as first-line treatment, demonstrating statistically significant improvements in both OS and PFS with the addition of tislelizumab. Patient-reported outcomes were notably favorable: by Cycle 4, clinically meaningful improvements were observed in coughing, hemoptysis, chest pain, dyspnea, and global health status/quality of life, with GHS/QoL benefits reaching statistical significance by Cycle 6 — all with an acceptable safety profile. The DeLLphi-303 phase 1b study (NCT05361395) explored tarlatamab (10 mg IV Q2W) combined with atezolizumab or durvalumab as first-line maintenance following chemo-immunotherapy in 88 ES-SCLC patients across 30 centers. With a median follow-up of 18.4 months, median OS reached 25.3 months (95% CI: 20.3–not estimable). Serious adverse events occurred in 57% of patients, most notably cytokine release syndrome (24%), though no treatment-related deaths were reported.

In the second-line and relapsed settings, the NEJ045A phase II trial (jRCTs031200319) assessed durvalumab combined with carboplatin and etoposide — with dose-adjusted induction — followed by durvalumab maintenance in 57 previously untreated ES-SCLC patients with poor performance status (PS 2–3). The tolerability endpoint was met in both PS 2 (67%) and PS 3 (50%) cohorts, with 1-year survival rates of 50.0% and 18.2%, respectively, though grade ≥3 adverse events were observed in 93% of patients. A separate 48-patient second-line study evaluated nab-paclitaxel plus anlotinib (ANNAB group) versus nab-paclitaxel alone (NAP group) in relapsed SCLC patients who had previously received immune checkpoint inhibitor-based therapy. The ANNAB combination demonstrated statistically significant superiority across all efficacy endpoints: median PFS 6.0 vs. 4.7 months (p=0.0004), ORR 37.5% vs. 8.3% (p=0.0363), and median OS 10.0 vs. 7.3 months (p<0.0001), with no significant between-group differences in adverse events.

Real-world evidence has further contextualized these findings. A retrospective multicenter study of 76 ES-SCLC patients receiving first-line atezolizumab plus platinum-etoposide (2021–2025) reported an ORR of 81.67% (95% CI: 70.08–89.44%), median PFS of 7.2 months, and median OS of 9.4 months, broadly consistent with pivotal trial data. Grade ≥3 treatment-related adverse events occurred in 44.7% of patients, with no treatment-related deaths; ECOG PS ≥2, hepatic metastases, and age ≥65 years were independently associated with inferior survival. A real-world analysis of tarlatamab in 40 patients in the second-line setting highlighted the clinical significance of CRS and immune effector cell-associated neurotoxicity syndrome (ICANS), with prophylactic tocilizumab substantially reducing the incidence of both toxicities — underscoring the importance of proactive immune toxicity management protocols as this bispecific T-cell engager enters broader clinical use.

Targeting B7-H3: Risvutatug Rezetecan's Novel Approach in SCLC

The therapeutic landscape for advanced and relapsed SCLC has expanded considerably in recent years, with antibody-drug conjugates (ADCs) and bispecific T-cell engagers emerging as particularly promising modalities. ADCs — comprising a monoclonal antibody linked to a cytotoxic payload — achieve targeted tumor cell killing by exploiting surface antigen expression. In extensive-stage SCLC, primary ADC targets under clinical investigation include B7-H3, Trop-2, SEZ6, DLL3, and EGFR-HER3. Across ongoing trials, these agents have demonstrated encouraging efficacy signals, with objective response rates (ORRs) ranging from 33.3% to 68.0% and median progression-free survival (PFS) of 4.0 to 7.6 months. Concurrently, tarlatamab — a DLL3-CD3 bispecific T-cell engager — received FDA accelerated approval in May 2024 for ES-SCLC following progression on platinum-based chemotherapy. In the phase 2 DeLLphi-301 trial (NCT05060016), tarlatamab achieved an ORR of 40% (95% CI: 31%–51%) with a median duration of response of 9.7 months. Propensity score-weighted comparisons against real-world therapies further demonstrated a hazard ratio of 0.45 for overall survival (95% CI: 0.30–0.68) and an odds ratio of 2.80 for ORR (95% CI: 1.44–5.83), underscoring its clinical differentiation. Notably, tarlatamab carries a Boxed Warning for cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS).

Beyond these modalities, several targeted and chemotherapeutic strategies are addressing the challenge of platinum-resistant and relapsed disease. Lurbinectedin has been approved as a newer chemotherapeutic option for SCLC and represents an alternative for cisplatin-resistant patients. Additional resistance-focused approaches include multidrug resistance (MDR) inhibitors to restore tumor sensitivity, Bcl-2 family inhibitors targeting dysregulated apoptotic pathways, and PARP inhibitors — though the latter demonstrate variable efficacy shaped by genetic heterogeneity, biomarker expression, and microenvironmental factors. Immune checkpoint inhibitors targeting PD-1/PD-L1 and CTLA-4 continue to be investigated, albeit with efficacy constrained by the immunosuppressive tumor microenvironment and the characteristically rapid disease progression seen in SCLC.

Precision medicine approaches are increasingly informing patient stratification and treatment selection in this setting. Site-specific genomic correlations have been identified — MYC mutations with pleural metastasis, NTRK3 with brain metastasis, ALK with adrenal metastasis, and NTRK1 with intrapulmonary metastasis — suggesting actionable pathways for personalized therapeutic strategies. At the molecular phenotype level, three distinct SCLC subtypes have been characterized — proliferative, iNotch, and infiltrated — with the ANXA1-high subset of the infiltrated phenotype identified as a potential immunotherapeutic target, given its role in suppressing CD8+ T cells via M2 macrophage polarization. Preclinical and early clinical data further suggest that combining immunotherapy, targeted agents, and novel chemotherapeutics may synergistically enhance antitumor activity, with biomarker-guided patient selection poised to optimize outcomes as the therapeutic armamentarium for this aggressive malignancy continues to evolve.

Ris-Rez Navigates the Evolving SCLC Treatment Landscape

The SCLC therapeutic landscape remains challenging, with standard-of-care regimens—including platinum-based chemotherapy with or without immune checkpoint inhibitors (ICIs) such as atezolizumab or durvalumab—offering only modest survival benefits; median OS in extensive-stage disease rarely exceeds 12–15 months, and five-year OS remains as low as 5%. Multiple investigational strategies have been evaluated across disease settings, ranging from novel chemotherapy doublets and antiangiogenic combinations to CDK4/6 inhibitors and ICI-based regimens, with outcomes that are largely incremental. The table below summarizes key clinical data from published studies across the investigational and standard-of-care spectrum.

B7-H3 ADC Breakthrough: A New Horizon for SCLC Treatment

The announcement of positive Phase III results for risvutatug rezetecan (Ris-Rez) in advanced or relapsed small-cell lung cancer (SCLC) represents a pivotal moment for both the drug's developers and the broader oncology community. SCLC is an aggressive malignancy with a historically poor prognosis, and the demonstration of statistically significant and clinically meaningful improvements in overall survival (OS) compared to standard-of-care topotecan offers a much-needed new therapeutic avenue for patients.

Crucially, Ris-Rez is the first B7-H3-targeted antibody-drug conjugate (ADC) to achieve positive Phase III OS data in any tumor type. This validates B7-H3 as a promising and actionable target for ADCs, a class of therapeutics that has shown significant advantages in cancer treatment by combining the specificity of antibodies with potent cytotoxic payloads (PMID 35868498, 41052301). This success could pave the way for further development of B7-H3-targeting ADCs across a range of other cancers where this antigen is expressed.

However, as with all novel therapies, certain considerations are paramount. ADCs, while offering targeted delivery, are known to have specific class-related toxicities. These can include myelosuppression, gastrointestinal adverse events, and interstitial lung disease (ILD), as observed with other ADCs like trastuzumab deruxtecan and datopotamab deruxtecan (PMID 32469182, 41462360, 42042562). While the safety profile for Ris-Rez was reported as consistent with prior findings, careful monitoring and management of these potential side effects will be essential in clinical practice. Furthermore, the current data originates from a trial conducted in China, suggesting that additional studies may be required to fully assess its generalizability and secure regulatory approvals in other global markets. The potential for cancer cells to develop acquired resistance mechanisms to ADCs over time also remains a long-term challenge that will influence treatment sequencing and future combination strategies (PMID 42042562). Despite these considerations, the positive data for Ris-Rez underscores the transformative potential of ADCs and offers renewed hope for patients battling SCLC.