German biotechnology company MorphoSys has initiated its Phase II COSMOS trial of MOR208 combined with idelalisib (Zydelig) to treat adult patients with relapsed or refractory chronic lymphocytic leukaemia (CLL) or small lymphocytic lymphoma (SLL).

MOR208 is an investigational Fc-engineered monoclonal antibody targeting CD19.

Fc-modification of MOR208 results in potentiation of antibody-dependent, cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP), which is believed to improve a key mechanism of tumour cell killing.

MOR208 binds to CD19, which is broadly and homogeneously expressed across different B-cell malignancies, including DLBCL and CLL, thereby inducing direct apoptosis.

Idelalisib selectively inhibits phosphatidylinositol 3-kinase p110δ for CLL.

The Phase II CLL patients assessed for ORR & Safety in MOR208 Study (COSMOS) is being conducted as a single-arm, open-label, multicentre trial, which will include patients in Europe and the US who will receive intravenous infusions of MOR208 for up to 24 cycles of 28 days each and oral administration of Idelalisib on a twice-daily basis.

"We look forward to exploring the potential of MOR208 in this indication in combination with idelalisib."

MorphoSys chief development officer Dr Arndt Schottelius said: "There is a particularly high medical need for chronic lymphocytic leukaemia (CLL) patients, especially following discontinuation of a BTK inhibitor therapy.

“We look forward to exploring the potential of MOR208 in this indication in combination with idelalisib.”

The study is primarily focused on determining the overall response rate (ORR), as well as comprising complete responses (CR) and partial responses (PR) resulted by the MOR208 and Idelalisib combination.

The secondary endpoints of the study are to assess progression-free survival (PFS), overall survival (OS) and duration of response (DoR), evaluation of the drug combination's safety and determination of pharmacokinetic parameters of MOR208.

MOR208 is currently being tested as an immunotherapeutic treatment option within several phase II combination studies in patients with B-cell malignancies, while another Phase II Lenalidomide-MOR208 IN DLBCL (L-MIND) study is testing the safety and efficacy of MOR208 in combination with lenalidomide to treat relapsed or refractory DLBCL.