Re-challenge with catumaxomab in patients with malignant ascites: results from the SECIMAS study

Malignant ascites is a common phenomenon in cancer patients. It poses a great challenge to the clinician, because of limited treatment options and strong impairment of the quality of life of the often palliative patients. The SECIMAS study investigated the feasibility of a re-challenge with four catumaxomab intraperitoneal infusions in patients who had already received a first cycle of four infusions in the phase III CASIMAS study, which compared catumaxomab with and without prednisolone premedication. The primary endpoint was the proportion of patients who received at least three catumaxomab infusions. Secondary endpoints included a composite safety score (CSS) summarising the worst grades for the main catumaxomab-related adverse events (pyrexia, nausea, vomiting and abdominal pain), safety, efficacy and the occurrence of anti-drug antibodies (ADAs). Eight of nine screened patients received a second catumaxomab cycle. Compliance with a catumaxomab re-challenge was high: all eight patients (100%) received all four infusions. The median CSS was 3.0 versus 3.4 in CASIMAS. The tolerability profile of the second catumaxomab cycle was comparable to that of the first cycle. Median puncture-free survival (48 days) and overall survival (407 days) were longer than in CASIMAS (35 and 103 days, respectively), although median time to next puncture was shorter (60 vs. 97 days). Of six patients sampled, all were ADA positive at screening and remained ADA positive until the end of the study. The presence of ADAs did not affect catumaxomab's safety or efficacy. The CSS and tolerability profile for catumaxomab in SECIMAS were comparable to those in CASIMAS. The majority of patients benefitted from a second cycle of catumaxomab. A re-challenge seems to be feasible and safe for selected patients with recurrent malignant ascites due to carcinoma after a first cycle of catumaxomab.

Trifunctional bispecific antibodies induce tumor-specific T cells and elicit a vaccination effect

A major goal of tumor immunotherapy is the induction of long-lasting systemic T-cell immunity. Bispecific antibodies (bsAbs) that lack the immunoglobulin Fc region confer T-cell-mediated killing of tumor cells but do not induce long-term memory. In contrast, trifunctional bsAbs comprise an appropriate Fc region and, therefore, not only recruit T cells but also accessory cells that bear activating Fcγ receptors (FcγR), providing additional T-cell-activating signals and securing presentation of tumor-derived antigens to T cells. In this study, we show that trifunctional bsAbs induce a polyvalent T-cell response and, therefore, a vaccination effect. Mice were treated with melanoma cells and with a trifunctional bsAb directed against the melanoma target antigen ganglioside GD2 in addition to murine CD3. The trifunctional bsAb activated dendritic cells and induced a systemic immune response that was not replicated by treatment with the F(ab')2-counterpart lacking the Fc region. Restimulation of spleen and lymph node cells in vitro yielded T-cell lines that specifically produced interferon-γ in response to tumor. In addition, trifunctional bsAb-induced T cells recognized various specific peptides derived from melanoma-associated antigens. Moreover, these polyvalent responses proved to be tumor-suppressive and could not be induced by the corresponding bsF(ab')2-fragment. Taken together, our findings provide preclinical proof of concept that trifunctional bsAbs can induce tumor-specific T cells with defined antigen specificity.

Cancer therapy with trifunctional antibodies: linking innate and adaptive immunity

Trifunctional antibodies (trAbs) are promising novel anticancer biologics with a particular mode of action capable of linking innate with adaptive immunity. Based on their unique structure, trifunctional IgG-like heterodimeric antibodies, consisting of nonhuman mouse and rat immunoglobulin halves are able to redirect T lymphocytes, as well as accessory cells, to the tumor site. This recruitment of immune cells is accompanied by cellular activation events elicited by anti-CD3, as well as Fcγ-receptor engagement of trAbs supported by a proinflammatory Th1-biased cytokine milieu. All necessary immunological factors required for long-term vaccination-like effects are stimulated along trAb-mediated therapeutic interventions. Thus, the concerted interplay of antibody-dependent cellular cytotoxicity plus the polyclonal T-cell cytotoxicity and Fcγ-receptor-driven induction of long-lasting immune responses after the initial tumor cell elimination represent the major hallmarks of trAb-mediated treatment of malignant diseases.