ARGX-117 Development

ARGX-117 is a highly differentiated therapeutic monoclonal antibody targeting C2 equipped with our proprietary NHANCE mutations. By addressing a novel target at the intersection of the complement and lectin pathways of the complement cascade, we believe ARGX-117 represents a broad pipeline opportunity across several severe autoimmune indications. Activation of the classical and lectin pathway of complement may contribute to tissue damage and organ dysfunction in a number of autoimmune inflammatory diseases and ischemia-reperfusion conditions. Targeting C2 also leaves the alternative pathway of the complement system intact, which is an important component of the innate defense system.

ARGX-117 exhibits both pH- and calcium dependent binding. These unique characteristics enable ARGX-117 to capture free C2 in circulation and release it in the endosome to be sorted for degradation in the lysosome. ARGX-117 is equipped with NHANCE mutations increasing its affinity for FcRn and allowing it to recycle back into circulation to capture more C2.

We obtained the rights to ARGX-117 as part of our IIP. argenx and Broteio launched a collaboration in 2017 to conduct research, with support from the University of Utrecht, to demonstrate preclinical proof-of-concept of the mechanism of ARGX-117. Based on promising preclinical data generated under this collaboration agreement, we exercised the exclusive option to license the program and assumed responsibility for further development and commercialization.

In addition to an IV formulation, we have exclusive access to Halozyme’s ENHANZE^® SC drug delivery technology for the C2 target.

Phase 1 Data

We conducted a Phase 1 healthy volunteer clinical trial of IV and SC ARGX-117. This first-in-human clinical trial was a double-blind placebo-controlled study designed to assess the safety, tolerability, PK and PD of a broad dose range of ARGX-117 in 102 healthy subjects. In the single ascending dose part, we evaluated 70 subjects and tested up to 80 mg/kg administered IV and up to 60 mg/kg administered SC. In the MAD part of the study, we evaluated 32 subjects to understand the safety and tolerability of repeated administrations and in particular to generate a data-set to optimally inform a PK/PD model.

The majority of the observed TEAEs were categorized as grade 1 (or mild). Few grade 2 (or moderate) TEAE were observed and, in the MAD part of the study, no grade 2 or higher TEAEs were observed. Overall, we concluded that single and multiple administrations of ARGX-117 or placebo have a favorable safety and tolerability profile supporting the investigation of study drug in patient studies.

We observed a dose-dependent reduction of free C2 levels. After one dose of 30 mg/kg ARGX-117, free C2 levels were reduced by 95% for more than 100 days. In the MAD part of the study, we could reach full complement blockade with more than 99% reduction of free C2 levels.

Following analysis of Phase 1 data, and the observed favorable safety and tolerability profile and consistent PK/PD profile, we launched a Phase 2 proof-of-concept clinical trial in MMN in the fourth quarter of 2021 within our neuromuscular franchise. Proof-of-concept ARDA clinical trial is ongoing to evaluate safety, tolerability, and potential dosing regimen in MMN. Interim data from ARDA are expected in mid-2023.

Overview of MMN and Current Treatment

MMN is a debilitating neuromuscular autoimmune disorder that is characterized by slowly progressive muscle weakness due to motor neuron degeneration. It mainly affects hands and forearms, mainly in males, and the median age of diagnosis is around 40 years. Diagnosis takes about a year and a half and is usually misdiagnosed as amyotrophic lateral sclerosis (ALS). There are estimated to be around 13,000 patients with MMN in the U.S. and this number is increasing.

Specific pathophysiologic characteristics of MMN include the presence of IG M (IgM) autoantibodies against the ganglioside GM1 and conduction block, i.e., impaired propagation of action potentials along the axon. GM1 is widely expressed in the nervous system by neurons, particularly around the nodes of Ranvier, and Schwann cells.

IVIg is the only approved treatment for MMN and needs to be dosed regularly to address the disease’s progressive nature.

DGF and/or Allograft Failure

We intend to start a phase 2 proof-of-concept clinical trial in the second half of 2023 to evaluate ARGX-117 for the prevention of DGF (n) and/or allograft failure after kidney transplantation. This occurs in up to 40% of kidney transplant recipients and is often a result of ischemia reperfusion injury.

There is compelling evidence from kidney biopsies of mannose-binding lectin and C4d co-staining indicating involvement of both the classical and lectin pathways, making C2 an ideal target. Furthermore, there is a well-established process to measure kidney function and establish proof-of-concept and achieve registration. On this basis, combined with the significant unmet medical need, we have chosen DGF (n) and allograft failure after kidney transplantation as second indication for ARGX-117.

Dermatomyositis

In January 2023, we announced DM as the third indication for ARGX-117.