# MDX-1097

MDX-1097 (formerly called IST-1097, now called KappaMab) is a monoclonal antibody therapy that in 2023 has been assessed in a Phase IIb clinical trial in conjunction with lenalidomide and dexamethasone as a treatment for multiple myeloma, a type of white blood cell cancer. MDX-1097 was originally developed by scientists at Immune System Therapeutics Ltd. In 2015, Haemalogix Ltd acquired the rights to MDX-1097 and are taking it through clinical testing.

## Development

Originally, a mouse (murine) antibody was used for initial experiments. This murine monoclonal antibody, called K-1-21, was raised against purified human kappa Bence Jones proteins (BJP). K-1-21 was shown to be specific for a cell-surface antigen that was named kappa myeloma antigen (KMA). KMA was found on malignant B cells (plasma cells) isolated from the bone marrow of patients with kappa restricted multiple myeloma (kMM), lymphoma and Waldenström macroglobulinemia. KMA was also detected in cell culture on the surface of human myeloma cell lines derived from patients with kappa restricted myeloma (kHMCLs). The K-1-21 antibody was re-named mKap.
The next step was to produce an antibody for use in humans that was based on the murine version. The heavy and light chain variable region genes (VH and Vk) of MDX-1097 were isolated from mKap hybridoma cells using recombinant DNA methodologies. MDX-1097, a chimeric (murine plus human) monoclonal antibody, was manufactured according by Medarex Inc. (subsidiary of Bristol-Myers Squibb). MDX-1097 has retained the specificity and affinity observed for mKap. MDX-1097 has been used in the clinical trials described below, as well as in vitro studies.

## Pharmacology
### Mechanism of action

KMA is a membrane-bound form of free kappa light chain on malignant B-cells, in-vitro activated B cells and rare tonsillar B-cells. KMA is not found on normal human leucocytes. KappaMab (MDX-1097) is specific for KMA and binds to a unique conformational epitope in the kappa constant region that is presented when kappa free light chain (kFLC) associates with sphingomyelin in the cell membrane. KappaMab does not bind to kappa immunoglobulin (Igκ) and it has a 5-fold higher affinity for membrane-bound KMA (IC$_{50}$ 4nM) when compared to serum kappa Free Light Chain (IC$_{50}$ 20nM). Moreover, in vitro studies demonstrated that KM induces selective antibody-dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP) of kappa-positive MM cells and that lenalidomide (LEN) exposure upregulates KMA expression on MM cells promoting enhanced KM-induced NK-mediated ADCC.

## Clinical trials

In an initial Phase 1 clinical trial, MDX-1097 was administered intravenously to multiple myeloma patients with stable kappa-type disease, with doses ranging from 0.3 mg/kg to 10.0 mg/kg. The study primarily aimed to evaluate MDX-1097's safety profile across these dose levels.
In a Phase 2a clinical trial involving 19 patients with stable kappa-type multiple myeloma, MDX-1097 was administered at a dose of 10 mg/kg weekly for 8 doses to assess safety and efficacy.,
In a Phase 2b investigator-initiated clinical trial, repeated doses of KappaMab were administered either alone or in combination with lenalidomide and dexamethasone to patients with kappa-type relapsed, refractory multiple myeloma (MM). The study, conducted across multiple centers, aimed to assess safety and efficacy in both treatment cohorts.