Background/Purpose: P140 is a 21-mer peptide (sequence 131-151, phosphorylated at position 140) that is derived from the spliceosomal protein U1-70K. In a multicenter, randomized, placebo-controlled phase IIb study, P140/Lupuzor^TM had no adverse safety signals and met its primary efficacy end points in lupus patients¹. These results confirm data generated in MRL/lpr lupus-prone mice in which the preclinical studies were performed. We found previously that P140 reduces autophagic flux in MRL/lpr B cells² and that macroautophagy (the best characterized type of autophagy) is abnormally enhanced in T lymphocytes from lupus mice and patients³. More recently, we discovered that in MRL/lpr mice, P140 more precisely targets a selective form of autophagy, chaperone-mediated autophagy. We deciphered the successive steps of P140 action leading in fine to a decay of endogenous antigen processing and loading to MHCII molecules and as a consequence, to a lower activation of autoreactive T cells⁴. Here, the mechanism of action of P140 was further studied in peripheral cells from normal and lupus individuals.

Methods: Studies were performed ex vivo on B cells from normal donors and lupus patients. A scrambled peptide was used as control. Immunocytochemical analyses were applied to identify the way of P140 enters into B cells. The effect of P140 on MHCII molecules stability was studied using western immunoblotting (WB) and FACS analyses. FACS studies were used to evaluate the effect of P140 on the B cells differentiation into plasmablasts and plasma cells and on BCR signaling amplitude.  Microscopy and WB analyses were performed to study the effect of P140 on autophagy.

Results: P140 that is not immunogenic in lupus patients⁵ showed no direct effect on BCR signaling in normal B cells (mature, transitional, IgG/IgM memory). As in MRL/lpr mice, P140 enters human B cells via a clathrin-dependent endo-lysosomal pathway and induces a decrease of MHCII expression. Higher the SLEDAI score of patients was, higher the P140 effect was measurable. P140 did not induce apoptosis of B cells from healthy or lupus patients. The autophagic flux was affected in P140-treated B cells.

Conclusion: Our findings provide strong arguments to conclude that the mechanism of action of P140 peptide is similar in MRL/lpr mice and lupus patients. These results shed light on mechanisms by which P140/Lupuzor modulates lupus disease in humans affected by this disorder.

Refs: ¹Zimmer et al. ARD 2013; ²Page et al. ARD 2011; ³Gros et al. Autophagy 2012; ⁴Macri et al. Autophagy 2015; ⁵Schall & Muller Lupus 2015.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/autophagy-pathway-as-a-target-of-therapeutic-p140-peptide-used-in-lupus/