CS1001-304: A phase III study of fluorouracil and cisplatin (FP) with CS1001, an anti-PD-L1 antibody, or placebo in unresectable locally advanced, recurrent or metastatic esophageal squamous cell carcinoma (ESCC).

4037 Background: Fluoropyrimidine and platinum-based chemotherapy are considered first-line therapy options for patients with unresectable advanced or recurrent metastatic esophageal squamous cell carcinoma(ESCC). After fluoropyrimidine and platinum-based chemotherapy is failed, taxanes (docetaxel(DTX) and paclitaxel(PTX)) was mainly used as a second-line treatment for ESCC. Therefore, we conducted a trial to compare DTX and PTX in patients with unresectable advanced or recurrent ESCC who were failed to previous fluoropyrimidine and platinum-based chemotherapy. Methods: We did a randomized, an open-labeled and multicentre phase 2 study. Inclusion criteria included age 20 to 80 years with unresectable advanced or recurrent ESCC, Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1. Patients who were refractory to fluoropyrimidine and platinum-based chemotherapy. Treatment consisted of DTX 70 mg/m2 repeated every 21 days or PTX 100 mg/m2 once weekly on days 1, 8, 15, 22, 29, and 36 of a 49-day cycle. Results: 80 patients were enrolled between May 2012 and April 2019. 41 patients received DTX and 39 patients received PTX. After assessment of eligibility, two patients proved uneligible (one for double cancer, one for contraindication to DTX) and were excluded from the analysis. But, 80 patients were evaluable for the toxicity analyses. A median follow-up time was 32 months. Overall survival was significantly longer in the PTX group than in the DTX group (median, 8.8 months vs. 7.3 months; hazard ratio, 0.62; 95% CI, 0.38 to 0.9998; P = 0.047). The median progression-free survival was significantly longer in the PTX group than in the DTX group (median, 4.4 months vs. 2.1 months; hazard ratio, 0.49; 95% CI, 0.30 to 0.78; P = 0.002). The median time to treatment failure was significantly longer in the PTX group than in the DTX group (median, 3.8 months vs. 2.1 months; hazard ratio, 0.45; 95% CI, 0.28 to 0.73; P＜0.001). The most common adverse events of grade 3 or higher were a decreased neutrophil count (in 28% of the PTX group and in 80% of the DTX group). Febrile neutropenia was also more frequent in the DTX group than the PTX group (46％ vs. 0%). There was one death from sudden death in which treatment-related mortality could not be ruled out. Conclusions: Secound-line treatment with PTX, as compared with DTX, reduced the risk of ESCC. Clinical trial information: UMIN000007940.

363 Background: Platinum-based chemotherapy is the standard first-line treatment for advanced or metastatic ESCC. Recently, the combination of PD-(L)1 pathway blockade with chemotherapy has shown synergistic efficacy in a few clinical trials. SHR-1701 is a novel bifunctional fusion protein composed of a mAb against PD-L1 fused with the extracellular domain of TGF-β receptor II. The purpose of this ongoing phase II trial (ChiCTR2000039909) was to evaluate the efficacy and safety of SHR-1701 combined with chemotherapy for unresectable locally advanced, recurrent or metastatic ESCC in China. Methods: This trial enrolled systemic treatment-naive patients(pts) with histologically or cytologically confirmed unresectable locally advanced, recurrent or metastatic ESCC who had ECOG PS of 0-1. Eligible pts received SHR-1701 (30mg/kg, iv, d1, q3w) combined with up to 6 cycles of albumin-bound paclitaxel (125mg/m2, iv, d1, d8, q3w) and cisplatin (75mg/m2, iv, d1, q3w). For those without progressive disease, maintenance treatment was administrated with SHR-1701 monotherapy until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). Secondary endpoints included progression free survival (PFS), overall survival (OS), disease control rate (DCR), safety and biomarkers. Results: As of September 21, 2022, 18 pts were enrolled. The median age was 67.5 years (range: 46–75 years) and 16 (88.9%) were male. 10 of the pts (55.6%) presented with distant metastasis. 14 pts were included in the efficacy analysis and 17 were in the safety analysis. The ORR and DCR were 85.7% and 100.0%, respectively. One patient achieved a complete response (CR) which will reach confirmation at next visit. 11 pts had partial response (PR), including 9 confirmed PR, one pending confirmation PR, and one unconfirmed PR. In addition, one PR patient got a CR target lesion. Grade 3-4 treatment-related adverse events (AEs) were observed in 23.5% of pts, including neutropenia (11.8%), leukopenia (5.9%), anemia (5.9%), emesis (5.9%) and rash (5.9%). Immune-related AEs (irAEs) were observed in 52.9%, and only one grade 3 irAE of rash occurred. Conclusions: SHR-1701 plus chemotherapy showed potential clinical benefits with acceptable toxicity as first-line treatment, and it might be a favorable option for pts with advanced ESCC. Clinical trial information: ChiCTR2000039909 .

4035 Background: NIVO + chemo and NIVO + IPI demonstrated significant overall survival (OS) benefit vs chemo in previously untreated patients (pts) with advanced ESCC in the phase 3 CheckMate 648 study. We report expanded results from the primary analysis with 13-month (mo) minimum follow-up. Methods: Pts with previously untreated, unresectable advanced, recurrent, or metastatic ESCC were randomized to NIVO (240 mg Q2W) + chemo (fluorouracil + cisplatin Q4W), NIVO (3 mg/kg Q2W) + IPI (1 mg/kg Q6W), or chemo. Primary endpoints were OS and progression-free survival (PFS) per blinded independent central review (BICR) in pts with tumor cell programmed death ligand 1 (PD-L1) ≥ 1%. Secondary endpoints planned for hierarchical testing included OS, PFS, and objective response rate (ORR) per BICR in all randomized pts. Duration of response (DOR) per BICR and PFS2 per investigator (time from randomization to progression after subsequent systemic therapy, initiation of second subsequent systemic therapy, or death) were exploratory endpoints. Results: Among all pts randomized to NIVO + chemo (n = 321), NIVO + IPI (n = 325), or chemo (n = 324), PFS2 favored NIVO + chemo (HR 0.64, 95% CI 0.54–0.77) and NIVO + IPI (HR 0.74, 95% CI 0.62–0.88) vs chemo. ORR (95% CI) was 47% (42–53), 28% (23–33), and 27% (22–32), respectively. More responders with NIVO + chemo or NIVO + IPI vs chemo had prolonged DOR (≥12 mo; 39%, 48%, and 23%, respectively). Efficacy data by tumor cell PD-L1 and PD-L1 combined positive score will be presented. Grade 3/4 treatment-related adverse events with potential immunologic etiology (select TRAEs) occurred in ≤ 6% of pts with NIVO + chemo and NIVO + IPI, and non-endocrine select TRAEs resolved in 57%–95% of pts across organ categories (Table). Conclusions: NIVO + chemo and NIVO + IPI demonstrated favorable PFS2 and a higher proportion of pts with prolonged DOR vs chemo, as well as acceptable safety profiles. These results provide further support for each regimen as a new potential 1L standard of care in advanced ESCC. Clinical trial information: NCT03143153. [Table: see text]

BackgroundFirst‐line nivolumab plus chemotherapy and nivolumab plus ipilimumab both demonstrated significant overall survival (OS) benefit versus chemotherapy in previously untreated patients with advanced esophageal squamous cell carcinoma (ESCC) in the CheckMate 648 trial, leading to approvals of both nivolumab‐containing regimens in many countries. We report longer‐term follow‐up data.MethodsThis open‐label, phase III trial (NCT03143153) enrolled adults with previously untreated, unresectable, advanced, recurrent, or metastatic ESCC. Patients were randomized 1:1:1 to nivolumab plus chemotherapy, nivolumab plus ipilimumab, or chemotherapy. Primary endpoints were OS and progression‐free survival (PFS) by blinded independent central review. Hierarchical testing was performed first in patients with tumor cell programmed death ligand 1 (PD‐L1) expression of ≥1% and then in the overall population.ResultsA total of 970 patients were randomly assigned. After 29 months of minimum follow‐up, nivolumab plus chemotherapy continued to demonstrate improvement in OS versus chemotherapy (hazard ratio [HR] = 0.59 [95% CI: 0.46–0.76]) in patients with tumor cell PD‐L1 expression of ≥1% and in the overall population (HR = 0.78 [95% CI: 0.65–0.93]) and with nivolumab plus ipilimumab versus chemotherapy (HR = 0.62 [95% CI: 0.48–0.80]) in patients with tumor cell PD‐L1 expression of ≥1% and in the overall population (HR = 0.77 [95% CI: 0.65–0.92]). In patients with tumor cell PD‐L1 expression of ≥1%, nivolumab plus chemotherapy demonstrated PFS benefit versus chemotherapy (HR = 0.67 [95% CI: 0.51–0.89]); PFS benefit was not observed with nivolumab plus ipilimumab versus chemotherapy (HR = 1.04 [95% CI: 0.79–1.36]). Among all treated patients (n = 936), Grade 3–4 treatment‐related adverse events were reported in 151 (49%, nivolumab plus chemotherapy), 105 (32%, nivolumab plus ipilimumab), and 110 (36%, chemotherapy) patients.ConclusionsNivolumab plus chemotherapy and nivolumab plus ipilimumab continued to demonstrate clinically meaningful OS benefit versus chemotherapy with no new safety signals identified with longer follow‐up, further supporting use as first‐line standard treatment options for patients with advanced ESCC.

Although antiprogrammed death 1 antibody plus chemotherapy has recently been approved for first-line esophageal squamous cell carcinoma (ESCC), antiprogrammed death-ligand 1 antibody may offer another combination option in this setting. In this multicenter, randomized, double-blinded phase 3 trial a total of 540 adults (aged 18-75 years) with unresectable, locally advanced, recurrent or metastatic ESCC and who had not received systemic treatment were enrolled. All patients were randomized at 2:1 to receive either sugemalimab (an anti-PD-L1 antibody; 1,200 mg) or placebo every 3 weeks for up to 24 months, plus chemotherapy (cisplatin 80 mg m-2 on day 1 plus 5-fluorouracil 800 mg m-2 day-1 on days 1-4) every 3 weeks for up to six cycles. At the prespecified interim analysis this study had met dual primary endpoints. With a median follow-up of 15.2 months, the prolongation of progression-free survival was statistically significant with sugemalimab plus chemotherapy compared with placebo plus chemotherapy (median 6.2 versus 5.4 months, hazard ratio 0.67 (95% confidence interval 0.54-0.82), P = 0.0002) as assessed by blinded independent central review. Overall survival was also superior with sugemalimab chemotherapy (median 15.3 versus 11.5 months, hazard ratio 0.70 (95% confidence interval 0.55-0.90, P = 0.0076). A significantly higher objective response rate (60.1 versus 45.2%) as assessed by blinded independent central review was observed with sugemalimab chemotherapy. The incidence of grade 3 or above treatment-related adverse events (51.3 versus 48.4%) was comparable between the two groups. Sugemalimab plus chemotherapy significantly prolonged progression-free survival and overall survival in treatment-naïve patients with advanced ESCC, with no unexpected safety signal. The ClinicalTrials.gov identifier is NCT04187352 .

Chemotherapy options for patients with advanced esophageal cancer had been limited until immune checkpoint inhibitors (ICIs) were approved for this indication. In recent years, ICI alone and ICI-combined chemotherapy have been approved, which prolonged the overall survival (OS) of patients with advanced esophageal cancer. We retrospectively analyzed 265 patients with unresectable advanced, recurrent, or metastatic esophageal squamous cell carcinoma (ESCC) who received chemotherapy with and without ICIs at Tohoku University Hospital from January 2013 to March 2022. Cisplatin plus fluorouracil therapy was the most frequently administered regimen as first-line treatment, and their administration frequency did not significantly differ between before 2019 and after 2020. Nivolumab was the most frequently used treatment as second-line therapy since its first approval in 2020 (74%), whereas taxanes were the most frequently used regimen before 2019 (55%). The median OS was 13.9 months over the entire observation period. Among patients who received second-line therapy, those receiving ICIs at any line demonstrated significantly longer OS from the start of second-line treatment than the others (p = 0.03). Univariate analysis revealed that a G8 score of < 11 (hazard ratio: 1.62, p = 0.02) was a prognostic factor in patients aged ≥ 65 years. Among each components of the G8 score, a decrease in food intake, weight loss, impaired mobility, and self-perceived poor health status were shown to be particularly associated with shorter OS. Our real-world data demonstrated that ICI administration contributed to improved OS after initiating second-line treatment for unresectable, advanced, or recurrent ESCC. Additionally, we revealed that the G8 score could be a useful prognostic factor in elderly patients with advanced ESCC treated with chemotherapy.

LBA4001 Background: NIVO demonstrated superior overall survival (OS) vs chemo in previously treated patients (pts) with ESCC (ATTRACTION-3). We report OS and progression-free survival (PFS) from CheckMate 648, the first global phase III study to evaluate both an immuno-oncology (I-O)/chemo combination and an I-O/I-O combination in advanced ESCC. Methods: Adults with previously untreated, unresectable advanced, recurrent or metastatic ESCC were enrolled regardless of tumor cell PD-L1 expression. Pts were randomized to NIVO (240 mg Q2W) + chemo (fluorouracil + cisplatin Q4W), NIVO (3 mg/kg Q2W) + IPI (1 mg/kg Q6W), or chemo alone. Primary endpoints for both comparisons were OS and PFS per blinded independent central review (BICR) in pts with tumor cell PD-L1 ≥ 1%. Hierarchically tested secondary endpoints included OS and PFS in all randomized pts. Results: 970 pts were randomized to NIVO + chemo, NIVO + IPI, and chemo arms (49% with tumor cell PD-L1 ≥ 1%). With 13 months (mo) minimum follow-up, NIVO + chemo and NIVO + IPI led to statistically significant improvement in OS vs chemo in pts with tumor cell PD-L1 ≥ 1% and all randomized pts (Table). Statistically significant PFS benefit was also observed for NIVO + chemo vs chemo (HR 0.65 [98.5% CI 0.46–0.92]; P = 0.0023) in pts with tumor cell PD-L1 ≥ 1%. PFS in NIVO + IPI vs chemo in pts with tumor cell PD-L1 ≥ 1% did not meet the prespecified boundary for significance. The objective response rate (per BICR) was 53% (NIVO + chemo), 35% (NIVO + IPI), and 20% (chemo) in pts with tumor cell PD-L1 ≥ 1% and in all randomized pts was 47%, 28%, and 27%, respectively; longer median (95% CI) duration of response was observed vs chemo for pts with tumor cell PD-L1 ≥ 1%: 8.4 (6.9–12.4), 11.8 (7.1–27.4), and 5.7 (4.4–8.7) mo and for all randomized pts: 8.2 (6.9–9.7), 11.1 (8.3–14.0), and 7.1 (5.7–8.2) mo, respectively. No new safety signals were identified (Table). Conclusions: NIVO plus chemo and NIVO plus IPI both demonstrated superior OS vs chemo, along with durable objective responses and acceptable safety, in pts with advanced ESCC, and each represents a potential new 1L treatment option. Clinical trial information: NCT03143153. [Table: see text]

O-3 Nivolumab (NIVO) plus chemotherapy (chemo) or ipilimumab (IPI) vs chemo as first-line treatment for advanced esophageal squamous cell carcinoma (ESCC): Expanded efficacy and safety analyses from CheckMate 648

Background Platinum plus 5-fluorouracil (FP) is recognized as the standard regimen of palliative chemotherapy for recurrent or metastatic esophageal squamous cell carcinoma (ESCC). Although taxane is widely selected for 2nd line regimen, other options are very limited. In Japan, S-1 is available for esophageal cancer. In this retrospective study, we evaluated the efficacy of S-1 monotherapy for recurrent or metastatic (advanced) ESCC refractory or intolerable to FP. Methods The subjects of this study were 11 patients with advanced ESCC who received S-1 after failure of FP. The endpoints evaluating efficacy were overall survival (OS), progression free survival (PFS), and overall response rate (ORR) in patients with target lesions (TLs). Results The characteristics of the subjects were: median age 69 years, PS (0/1) 5/6, number of prior chemotherapy regimens (1/2/3 ≥ ) 4/4/3. 9 patients were refractory and 2 were intolerant to prior FP. 9 patients had good control of the primary lesions. Only 2 patients received post-S-1 therapy. The median OS and PFS were 11.7and 3.0 months. Two of 9 patients with TLs, one refractory and the other intolerant to prior FP, achieved partial response (PR) while the remaining 7 patients showed progressive disease (ORR 22%). The other 2 patients without TLs showed nonCR/nonPD. Common treatment-related adverse events included grade 3 leukopenia for 1 patients (9.1%), but there were no serious cases. Conclusion ORR of 22% suggests modest activity of S-1 for advanced ESCC refractory or intolerable to platinum plus 5-FU (FP). However, more than half of the patients showed progressive disease. Future study exploring optimal patient selection for S-1 is warranted. Disclosure All authors have declared no conflicts of interest.

4062 Background: The prognosis of pts with advanced esophageal squamous cell carcinoma (ESCC) remains dismal clinically. Paclitaxel and cisplatin were used as the standard first-line regimen in ESCC for almost two decades. Recently, the combination of PD-1/PD-L1 pathway blockades with chemotherapy has shown synergistic efficacy in a few clinical trials. KN046 is the world's first dual immune checkpoint inhibitor, which can block PD-1/PD-L1 and CTLA-4 pathways at the same time. The purpose of this ongoing phase II trial (NCT03925870) in China was to evaluate the efficacy and safety of KN046 monotherapy or combined with chemotherapy for unresectable locally advanced, recurrent or metastatic ESCC. Methods: This trial included 3 cohorts, one of which enrolled systemic treatment naïve pts with histologically or cytologically confirmed unresectable locally advanced, recurrent or metastatic ESCC who have ECOG PS of 0-1. Eligible subjects were given paclitaxel (135-175mg/m2, iv, d1, q3w) and cisplatin (75mg/m2, iv, d2-4, q3w) plus KN046 (5mpk, iv, d1, q3w) for 4̃6 cycles during initial therapy. For those without progressive disease, maintenance treatment was administrated with KN046 monotherapy (5mpk, iv, q2w) until progression or unacceptable toxicity. Tumour response was assessed according to RECIST 1.1 every 6 weeks. The primary endpoint was investigator-assessed ORR. Secondary endpoints included DCR, safety, PK profile, and immunogenicity. Results: As of December 14, 2020, 15 pts were enrolled, all of them were male, 52.3% ≥60 years, 64% ECOG 1, 80% with distant metastasis. Median exposure time to KN046 was 11.4 wks and average KN046 treatment was 2.4 cycles. 12 pts were included in the efficacy analysis and 15 pts in the safety analysis. The overall response rate (ORR) and disease control rate (DCR) were 58.3% and 91.6%, respectively. 7 pts (58.3%) had partial response (PR) including one complete response of target lesion. 4 pts (33.3%) had stable disease (SD) with 3 pts showing more than 20% of tumor burden reduction. The overall incidence of KN046 related adverse events was 80.0%, with 13.3% Gr 3 or above TRAE. Infusion-related adverse events occurred during 7.8% and most were mild. Immune related adverse events（irAE）were seen in 53.3% and the most common Gr 3 irAE were nausea (n＝1, 6.7%) and rash (n＝1, 6.7%). Conclusions: KN046 plus paclitaxel/cisplatin demonstrated clinical efficacy and acceptable safety as first-line treatment, and might be a favorable option for pts with advanced ESCC. Clinical trial information: NCT03925870. Research Sponsor: Jiangsu Alphamab Biopharmaceuticals Co., Ltd. Clinical trial information: NCT03925870.

Background: China has the largest population of patients with esophageal cancer in the world. The major histopathological type is squamous cell carcinoma and it accounts for more than 90% of the cases. About 40% esophageal squamous cell carcinoma (ESCC) are PD-L1 positive, however, the prognostic and predictive value of this biomarker remains elusive for this disease. Regardless of PD-L1 status, the median overall survival of patients with advanced or metastatic ESCC is about 10 months, reflecting an unmet medical need for new treatments. Sintilimab is a fully human anti-PD-1 monoclonal antibody that blocks the PD-1/PD-L1,PD-L2 interaction and restores T-cell response thereby destroying tumor cells. Sintilimab has a safety profile consistent with other approved PD-1 antibodies and was approved for relapsed/refractory Hodgkin lymphoma in China in 2018. Recently, comparing to chemotherapy, nivolumab and pembrolizumab significantly improved overall survival in second-line esophageal cancer patients, which suggests the application of PD-1 therapy in first-line ESCC. This randomized, multicenter, double-blind, Phase III study compares the efficacy and safety of sintilimab in combination with paclitaxel and cisplatin (TP) versus placebo with TP as first-line systemic treatment in patients with unresectable, locally advanced or metastatic ESCC in China. Methods: To be eligible, patients must be between 18 and 75 years of age, not eligible for definitive therapy, have untreated locally advanced recurrent or metastatic ESCC, have at least one measurable lesion, and must provide tumor tissue for PD-L1 assessment (tumor proportion score, TPS by Dako 22 C3) within 6 months prior to entrance. Patients with prior PD-1, PD-L1 or PD-L2 antibody treatment, cisplatin cumulative exposure ≥ 300 mg/m2, or esophageal or tracheal stent placement are excluded. A total of 640 subjects will be randomized in a 1:1 ratio to receive either sintilimab plus TP Q3W or placebo plus TP Q3W until unacceptable toxicity, disease progression, death or withdrawal of consent. Stratifying factors include PD-L1 TPS ≥ 10% or &amp;lt; 10%, liver metastasis or not, and ECOG PS 0 or 1. The primary endpoint is median overall survival assessed in the experimental and control groups in both the entire population and the PD-L1 positive (TPS ≥ 10%) population. The secondary endpoints are PFS, ORR, DCR, DoR and safety. Clinical trial information: NCT03748134. Citation Format: Lin Shen, Zhihao Lu, Linxinyu Xu, Yan Wang, Hui Zhou, Ying Liu. ORIENT-15: A randomized, multicenter, double-blind, Phase III study of sintilimab + paclitaxel and cisplatin (TP) versus placebo + TP as first-line treatment in patients with unresectable locally advanced or metastatic esophageal squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT211.

215 Background: Esophageal squamous cell carcinoma (ESCC) is a lethal cancer with a high unmet medical need. Camrelizumab, an anti-PD-1 monoclonal antibody, significantly improved overall survival (OS) and objective response rate (ORR) in Chinese patients (pts) with advanced ESCC compared with chemotherapy, with a manageable safety profile in phase III randomized trial (ESCORT). However, the absolute long-term survival benefiting from PD-1 inhibitors is limited, and new effective treatments are needed. Here, our study aimed to assess the efficacy and safety of combination with camrelizumab and apatinib (VEGFR2 inhibitor) as second-line treatment for advanced ESCC. Methods: This ongoing phase II trial (NCT03736863) in six sites in China enrolled pts aged 18-75 with unresectable locally advanced, locally recurrent, or metastatic ESCC that progressed or were intolerant after first-line chemotherapy, and an ECOG performance status of 0-1. Pts received 200 mg intravenous camrelizumab every two weeks plus 250 mg oral apatinib daily in 4-week cycles until disease progression, unacceptable adverse events (AEs) or withdrawal of consent. The primary endpoint was investigator-assessed ORR. Secondary endpoints included disease control rate (DCR), progression-free survival (PFS) and OS. Results: At data cutoff (Sept 11, 2020), 36 pts were enrolled, 7 females and 29 males, and 25 pts had lymph node metastases. Twelve pts received radiotherapy and 25 underwent surgery. Twenty-five pts were included in the efficacy analysis with median follow-up time of 5.0 months and 36 pts in the safety analysis with median follow-up time of 4.6 months. The primary endpoint ORR without confirmation was 40 % with complete response in two pts (8%) and partial response in eight pts (32%). Thirteen pts (52%) had stable disease, and the DCR was 92%. The median PFS and OS were not reached. A total of 72.2% of pts had AEs, and 30.6% of pts experienced grade 3 AEs. The most common AEs (all grade, grade≥3) were elevated aspartate aminotransferase (30.6%, 19.4%), elevated alanine aminotransferase (30.6%, 13.9%), hypertension (25%, 2.8%),neutrophil (25%, 5.6%), thrombocytopenia (25%, 0%), leukopenia (22.2%, 2.8%), anemia (11.1%, 0%), proteinuria (11.1%, 0%), hematochezia (8.3%, 0%), reactive cutaneous capillary endothelial proliferation (5.6%, 2.8%), pruritus (5.6%, 0%), esophageal fistula (5.6%, 0%), fatigue (2.8%, 0%) and hypothyroidism (2.8%, 0%). Conclusions: This is the first study to explore the combination of PD-1 inhibitor and anti-angiogenesis inhibitor as a second-line treatment for advanced ESCC. Camrelizumab plus apatinib demonstrated encouraging clinical efficacy and acceptable safety as second-line treatment, and might be a favorable option for pts with advanced ESCC. Further phase III randomized trials are warranted. Clinical trial information: NCT03736863.

TPS4209 Background: There is a substantial need for more effective and tolerable first-line treatment options for patients with advanced ESCC. B7-H3 is a type 1 transmembrane protein that is highly expressed in several cancers, including ESCC, and is associated with a poor prognosis. Ifinatamab deruxtecan (I-DXd; formerly DS-7300a/MK-2400) is a B7-H3–directed antibody-drug conjugate comprising a humanized anti–B7-H3 IgG1 monoclonal antibody (ifinatamab) covalently linked to a potent topoisomerase I inhibitor payload (DXd; an exatecan derivative) by a cleavable linker. In the phase 1/2 DS7300-A-J101 study, I-DXd monotherapy showed promising antitumor activity in participants (pts) with advanced ESCC. KEYMAKER-U06 is an open-label, phase 1/2, umbrella platform study designed to evaluate investigational agents with or without pembrolizumab and/or chemotherapy for advanced gastroesophageal cancer. Substudy 06E (NCT06780111) will be conducted to evaluate I-DXd plus pembrolizumab with or without chemotherapy as first-line therapy for advanced ESCC. Methods: Eligible pts are aged ≥18 years with previously untreated, histologically or cytologically confirmed, locally advanced unresectable or metastatic ESCC, measurable disease per RECIST v1.1 by investigator review and verified by blinded independent central review (BICR), and an Eastern Cooperative Oncology Group performance status of 0 or 1. Pts will be assigned to 1 of 4 treatment arms: arm 1 (reference treatment; pembrolizumab 200 mg IV Q3W for ≤35 cycles plus chemotherapy [mFOLFOX6: oxaliplatin 85 mg/m 2 IV Q2W plus 5-FU 400 mg/m 2 (bolus) and 2400 mg/m 2 (continuous) IV Q2W plus leucovorin 400 mg/m² IV Q2W]); arm 2 (I-DXd 12 mg/kg IV Q3W plus pembrolizumab); arm 3 (I-DXd 12 mg/kg plus pembrolizumab plus 5-FU 400 mg/m 2 [bolus] and 2400 mg/m 2 [continuous] IV Q2W plus leucovorin 400 mg/m² IV Q2W); and arm 4 (I-DXd [8 mg/kg or 12 mg/kg] IV plus pembrolizumab plus 5-FU 2400 mg/m 2 IV and oxaliplatin 60 mg/m 2 ). Approximately 209 pts will be enrolled. A safety lead-in phase with ≤29 pts will be conducted in arms 2 (n ≤6), 3 (n ≤10), and 4 (n ≤13) using a Bayesian optimal interval design to confirm the safety and recommended phase 2 dose (RP2D; arm 4 only) of I-DXd in combination with other agents; this phase will be conducted sequentially, starting with arm 2, followed by arms 3 and 4. Thereafter, ≤180 pts will be included in the randomized phase (≤60 in arm 1; ≤40 each in arms 2-4). Pts will be randomly assigned 1:2 to arm 1 and the investigational arms. Primary outcomes are safety and tolerability, RP2D of I-DXd, and objective response rate per RECIST v1.1 by BICR for the selected dose. Secondary outcomes include DOR and PFS per RECIST v1.1 by BICR, OS, and pharmacokinetics of I-DXd in combination with other agents. Enrollment is ongoing. Clinical trial information: NCT06780111 .

TPS462 Background: Esophageal squamous cell carcinoma (ESCC) is the predominant histological subtype of esophageal cancer, particularly in Asian countries. Inhibition of the PD-1/PD-L1 axis has demonstrated antitumor activity in patients with advanced unresectable or metastatic ESCC. Tislelizumab, an investigational humanized IgG4 monoclonal antibody with high affinity and binding specificity for PD-1, was engineered to minimize binding to FcγR on macrophages in order to abrogate antibody-dependent phagocytosis, a mechanism of T-cell clearance and potential resistance to anti-PD-1 therapy. Results from early phase clinical studies suggest tislelizumab, as a single agent or in combination with chemotherapy, was generally well tolerated and had antitumor activity in patients with solid tumors, including ESCC. Methods: This global, phase 3, randomized, placebo-controlled, double-blind study (NCT03783442) is designed to evaluate the efficacy and safety of tislelizumab plus chemotherapy as first-line treatment of unresectable, locally advanced recurrent or metastatic ESCC. Adult patients with histologically confirmed unresectable ESCC, or locally advanced recurrent/metastatic disease with a ≥6 month treatment-free interval, are eligible; palliative radiation administered &gt; 4 weeks from study initiation is allowed. Patients who received prior anti-PD-(L)1, anti-PD-L2, or first-line therapy are ineligible. Patients (n≈480) will be randomized 1:1 to receive tislelizumab 200 mg IV every 3 weeks (Q3W) plus investigator-chosen chemotherapy (ICC) or placebo plus ICC. ICC options include: platinum (plat; cisplatin 60-80 mg/m2 or oxaliplatin 130 mg/m2 IV Q3W) + 5-FU 750-800 mg/m2 by continuous IV infusion over 24 hours for 5d Q3W; or plat + capecitabine 1000 mg/m2 orally BID for 14d Q3W; or plat + paclitaxel 175 mg/m2 IV Q3W. Progression-free and overall survival are primary endpoints; secondary endpoints include objective response rate, duration of response, and health-related quality of life. Safety will be assessed by monitoring adverse events, physical examinations, vital signs, and electrocardiograms. This study is actively enrolling. Clinical trial information: NCT03783442.

4034 Background: NIVO + chemo and NIVO + IPI are approved for the treatment of advanced ESCC in the US, EU, Japan, and many other countries based on the results from CheckMate 648 (NCT03143153). Here, we report 45-mo follow-up results. Methods: Adults with previously untreated, unresectable advanced, recurrent, or metastatic ESCC were randomized to NIVO (240 mg Q2W) + chemo (fluorouracil + cisplatin Q4W), NIVO (3 mg/kg Q2W) + IPI (1 mg/kg Q6W) or chemo. The primary endpoints were overall survival (OS) and progression-free survival (PFS) per blinded independent central review (BICR) in patients (pts) with tumor cell programmed death ligand 1 (PD-L1) ≥ 1%. Results: In total, 970 pts were randomized to NIVO + chemo, NIVO + IPI, or chemo. With 45-mo minimum follow-up, NIVO + chemo and NIVO + IPI demonstrated continued OS benefit and higher 45-mo OS rates vs chemo in pts with tumor cell PD-L1 ≥ 1% and all randomized pts (Table). Duration of response (DOR) was longer (Table) and the proportion of responders with DOR ≥ 45 mo was greater with NIVO + chemo and NIVO + IPI vs chemo in pts with tumor cell PD-L1 ≥ 1% (7% and 23% vs 0%, respectively) and all randomized pts (14% and 18% vs 6%). Any-grade treatment-related adverse events (TRAEs) occurred in 96% of pts with NIVO + chemo, 80% with NIVO + IPI, and 90% with chemo; grade 3/4 TRAEs occurred in 49%, 33%, and 37% of pts, respectively. No additional TRAEs leading to discontinuation and no new treatment-related deaths were reported with longer follow-up. Conclusions: After 45 mo of follow-up, NIVO + chemo and NIVO + IPI continued to demonstrate clinically meaningful survival benefit and more durable responses vs chemo, with no new safety signals. These results further support NIVO + chemo and NIVO + IPI as 1L treatment options for advanced ESCC. Clinical trial information: NCT03143153 . [Table: see text]