APL-1

The treatment of paroxysmal nocturnal hemoglobinuria (PNH) was revolutionized by the introduction of the anti-C5 agent eculizumab, which resulted in sustained control of intravascular hemolysis, leading to transfusion avoidance and hemoglobin stabilization in at least half of all patients. Nevertheless, extravascular hemolysis mediated by C3 has emerged as inescapable phenomenon in PNH patients on anti-C5 treatment, frequently limiting its hematological benefit. More than 10 years ago we postulated that therapeutic interception of the complement cascade at the level of C3 should improve the clinical response in PNH. Compstatin is a 13-residue disulfide-bridged peptide binding to both human C3 and C3b, eventually disabling the formation of C3 convertases and thereby preventing complement activation via all three of its activating pathways. Several generations of compstatin analogs have been tested in vitro, and their clinical evaluation has begun in PNH and other complement-mediated diseases. Pegcetacoplan, a pegylated form of the compstatin analog POT-4, has been investigated in two phase I/II and one phase III study in PNH patients. In the phase III study, PNH patients with residual anemia already on eculizumab were randomized to receive either pegcetacoplan or eculizumab in a head-to-head comparison. At week 16, pegcetacoplan was superior to eculizumab in terms of hemoglobin change from baseline (the primary endpoint), as well as in other secondary endpoints tracking intravascular and extravascular hemolysis. Pegcetacoplan showed a good safety profile, even though breakthrough hemolysis emerged as a possible risk requiring additional attention. Here we review all the available data regarding this innovative treatment that has recently been approved for the treatment of PNH.

Induction of tolerance to autoantigens in vivo is a complex process that involves several mechanisms such as the induction of regulatory T cells and changes in the cytokine and chemokine profiles. This approach represents an attractive alternative for treatment of autoimmune diseases. APL-1 is an altered peptide ligand derived from a novel CD4 + T cell epitope of human heat-shock protein of 60 kDa (HSP60), an autoantigen involved in the pathogenesis of rheumatoid arthritis (RA). We have shown previously that this peptide efficiently inhibited the course of adjuvant-induced arthritis in Lewis rats and induced regulatory T cell (Treg) in ex vivo assay with PBMC isolated from RA patients. This study was undertaken to evaluate the therapeutic effect of APL-1 and its combination with methotrexate (MTX) in collagen-induced arthritis (CIA). CIA was induced in male DBA/1 mice at 8 weeks of age by immunization with chicken collagen. APL, MTX or both were administrated beginning from arthritis onset. Therapeutic effect was evaluated by arthritis and joint pathologic scores. In addition, TNFα and IL-10 in sera were measured by ELISA. Treg induction was assessed by FACS analysis. APL-1 inhibits efficiently the course of arthritis in CIA, similar to MTX. In addition, therapy with APL-1 plus MTX reduced CIA in mice, associated with an increase in Treg. These facts reinforce the therapeutic possibilities of APL-1 as a candidate drug for treatment of RA.