Background: Claudin 18.2 (CLDN18.2) is contained within normal gastric mucosa epithelial tight junctions; upon malignant transformation, CLDN18.2 epitopes become exposed. Zolbetuximab, a chimeric monoclonal antibody, mediates specific killing of CLDN18.2-positive cells through immune effector mechanisms. Patients and methods: The FAST study enrolled advanced gastric/gastro-oesophageal junction and oesophageal adenocarcinoma patients (aged 18 years) with moderate-to-strong CLDN18.2 expression in 40% tumour cells. Patients received first-line epirubicin þ oxaliplatin þ capecitabine (EOX, arm 1, n ¼ 84) every 3 weeks (Q3W), or zolbetuximab þ EOX (loading dose, 800 mg/m 2 then 600 mg/m 2 Q3W) (arm 2, n ¼ 77). Arm 3 (exploratory) was added after enrolment initiation (zolbetuximab þ EOX 1000 mg/m 2 Q3W, n ¼ 85). The primary endpoint was progression-free survival (PFS) and overall survival (OS) was a secondary endpoint. Results: In the overall population, both PFS [hazard ratio (HR) ¼ 0.44; 95% confidence interval (CI), 0.29-0.67; P < 0.0005] and OS (HR ¼ 0.55; 95% CI, 0.39-0.77; P < 0.0005) were significantly improved with zolbetuximab þ EOX (arm 2) compared with EOX alone (arm 1). This significant PFS benefit was retained in patients with moderate-tostrong CLDN18.2 expression in 70% of tumour cells (HR ¼ 0.38; 95% CI, 0.23-0.62; P < 0.0005). Significant improvement in PFS was also reported in the overall population of arm 3 versus arm 1 (HR ¼ 0.58; 95% CI, 0.39-0.85; P ¼ 0.0114) but not in high CLDN18.2-expressing patients; no significant improvement in OS was observed in either population. Most adverse events (AEs) related to zolbetuximab þ EOX (nausea, vomiting, neutropenia, anaemia) were grade 1-2. Grade 3 AEs showed no substantial increases overall (zolbetuximab þ EOX versus EOX alone). Conclusions: In advanced gastric/gastro-oesophageal junction and oesophageal adenocarcinoma patients expressing CLDN18.2, adding zolbetuximab to first-line EOX provided longer PFS and OS versus EOX alone. Zolbetuximab þ EOX was generally tolerated and AEs were manageable. Zolbetuximab 800/600 mg/m 2 is being evaluated in phase III studies based on clinical benefit observed in the overall population and in patients with moderate-to-strong CLDN18.2 expression in 70% of tumour cells.

Celltrion Inc.

PurposeNeoadjuvant CT-P6, a trastuzumab biosimilar, demonstrated equivalent efficacy to reference trastuzumab in a phase 3 trial of HER2-positive early-stage breast cancer (EBC) (NCT02162667). We report post hoc analyses evaluating pathological complete response (pCR) and breast pCR alongside additional efficacy and safety measures.MethodsFollowing neoadjuvant treatment and surgery, patients received adjuvant CT-P6 or trastuzumab (6 mg/kg) every 3 weeks for ≤ 1 year.ResultsIn total, 271 and 278 patients received CT-P6 and trastuzumab, respectively. pCR and breast pCR rates were comparable between treatment groups regardless of age, region, or clinical stage. Overall, 47.6% (CT-P6) and 52.2% (trastuzumab) of patients experienced study drug-related treatment-emergent adverse events (TEAEs), including 17 patients reporting heart failure (CT-P6: 10; trastuzumab: 7). Two CT-P6 and three trastuzumab patients discontinued adjuvant treatment due to TEAEs.ConclusionAdjuvant CT-P6 demonstrated comparable efficacy and safety to trastuzumab at 1 year in patients with HER2-positive EBC, supporting CT-P6 and trastuzumab comparability.Electronic supplementary materialThe online version of this article (10.1007/s00280-019-03920-4) contains supplementary material, which is available to authorized users.

No abstract

510 Background: CT-P6 (C) is a proposed biosimilar to trastuzumab. This trial (NCT02162667) evaluated the similarity of C and trastuzumab in efficacy and safety for HER2+ EBC. Methods: 549 patients with HER2+ EBC were randomized to receive C (n=271) or trastuzumab (n=278) in combination with docetaxel (Cycles 1-4) and 5-fluorouracil, epirubicin, and cyclophosphamide (Cycles 5-8). C or trastuzumab was administered at 8 mg/kg (Cycle 1 only) followed by 6 mg/kg every 3 weeks. The primary endpoint was pathological complete response (pCR) rate at surgery. Secondary endpoints were overall response rate (ORR), PK, PD and safety. After surgery, patients received adjuvant C or trastuzumab to complete a total of 1-year treatment. Results: The pCR rate was 46.8% for C and 50.4% for trastuzumab. The 95% CIs for the risk ratio estimate were within the equivalence margin (0.74, 1.35) in PPS and ITT analyses. Other efficacy endpoints were similar between C and trastuzumab. The proportion of patients with at least 1 treatment-emergent SAE was 6.6% for C and 7.6% for trastuzumab. Only 1 patient in each group withdrew treatment due to significant LVEF decrease. Infusion-related reaction was reported for 8.5% of patients in C and 9.0% of patients in trastuzumab. Conclusions: This study demonstrated the similarity of efficacy in terms of pCR between CT-P6 and trastuzumab in EBC patients. Secondary efficacy endpoints also supported the similarity between CT-P6 and trastuzumab. CT-P6 was well tolerated with a similar safety profile to that of trastuzumab during the neoadjuvant period. Clinical trial information: NCT02162667. [Table: see text]