Humoral response to catumaxomab correlates with clinical outcome: results of the pivotal phase II/III study in patients with malignant ascites

The trifunctional antibody catumaxomab is a targeted immunotherapy for the intraperitoneal treatment of malignant ascites. In a Phase II/III trial in cancer patients (n = 258) with malignant ascites, catumaxomab showed a clear clinical benefit vs. paracentesis and had an acceptable safety profile. Human antimouse antibodies (HAMAs), which could be associated with beneficial humoral effects and prolonged survival, may develop against catumaxomab as it is a mouse/rat antibody. This post hoc analysis investigated whether there was a correlation between the detection of HAMAs 8 days after the fourth catumaxomab infusion and clinical outcome. HAMA-positive and HAMA-negative patients in the catumaxomab group and patients in the control group were analyzed separately for all three clinical outcome measures (puncture-free survival, time to next puncture and overall survival) and compared to each other. There was a strong correlation between humoral response and clinical outcome: patients who developed HAMAs after catumaxomab showed significant improvement in all three clinical outcome measures vs. HAMA-negative patients. In the overall population in HAMA-positive vs. HAMA-negative patients, median puncture-free survival was 64 vs. 27 days (p < 0.0001; HR 0.330), median time to next therapeutic puncture was 104 vs. 46 days (p = 0.0002; HR 0.307) and median overall survival was 129 vs. 64 days (p = 0.0003; HR 0.433). Similar differences between HAMA-positive and HAMA-negative patients were seen in the ovarian, nonovarian and gastric cancer subgroups. In conclusion, HAMA development may be a biomarker for catumaxomab response and patients who developed HAMAs sooner derived greater benefit from catumaxomab treatment.

Intraperitoneal treatment with the trifunctional bispecific antibody Catumaxomab in patients with platinum-resistant epithelial ovarian cancer: a phase IIa study of the AGO Study Group

OBJECTIVE

The aim of this study was to select the best catumaxomab regimen for further investigation in ovarian cancer based on confirmed tumour response.

METHODS

Randomised open-label phase IIa study in women with platinum-resistant or -refractory epithelial ovarian cancer. Catumaxomab (6-hour intraperitoneal infusion on days 0, 3, 7 and 10) was administered at a low (10, 10, 10 and 10 μg) or high dose (10, 20, 50 and 100 μg). Responders were patients with either a complete (CR) or partial (PR) response.

RESULTS

Forty-five patients were randomised to receive either low dose (23) or high dose (22). There were no responders in the low-dose versus one patient (5%) in the high-dose group with a PR. In the low-dose group, two patients (9%) had stable disease compared with five patients (23%) in the high-dose group. Catumaxomab was well tolerated and there was no difference between the dose groups in the incidence of treatment-induced adverse events, the most common of which were gastrointestinal and injection-site reactions.

CONCLUSION

Catumaxomab had modest activity in platinum-resistant ovarian cancer. The high-dose regimen was associated with a slightly better therapeutic index than the low dose regimen.