Complement Blockade with a C1 Esterase Inhibitor in Paroxysmal Nocturnal Hemoglobinuria | Aplastic Anemia & MDS International Foundation Return to top.

Complement Blockade with a C1 Esterase Inhibitor in Paroxysmal Nocturnal Hemoglobinuria

Original Publication Date: 
Friday, January 31, 2014

Note: This review is based upon a presentation at the 2013 American Society of Hematology (ASH) Annual Meeting, December 7-10 in New Orleans, Louisiana.The full abstract may be reviewed on the ASH Annual Meeting Web site. Search by entering the title in the search box. The abstract number is referenced to access the full report.

Abstract # 594

Amy E. DeZern, M.D., M.H.S., Marc Uknis, M.D., Ph.D., Galina Mukhina, M.D., Ph.D., Jo Anne Saye, Ph.D., Jeffrey J. Pu, M.D., Ph.D., and Robert Brodsky, M.D.

Patients with paroxysmal nocturnal hemoglobinuria (PNH) don’t have two important proteins, CD55 and CD59, that normally protect red blood cells from destruction by the complement system. The proteins in the complement system normally fight foreign invaders, such as viruses, in the body. Eculizumab (Soliris®) compensates for the CD59 but not the CD55 deficiency in people with PNH. But many patients treated with eculizumab have C3 (a protein in the complement system) on the surface of their red blood cells, and those with higher numbers of C3-positive cells tend to have more immature red blood cells and a poorer response to eculizumab.

This study focused on C1 esterase inhibitor (C1 INH), a protein that inhibits complement and prevents C3 deposits on the red blood cells of patients with PNH who are treated with eculizumab. The authors examined the effects of C1 INH on premature red blood cell destruction in blood samples from 5 patients with PNH and 3 healthy donors. 

Key findings:

  • C1 INH treatment reduced the amount of C3 deposited on red blood cells from patients with PNH that lacked the CD55 protein.
  • C1 INH treatment prevented premature destruction of C3-positive red blood cells in samples from all 5 patients with PNH.


  • C1 INH stops C3 from being deposited on red blood cells lacking the CD55 protein from patients with PNH who are undergoing treatment with eculizumab.
  • Inhibiting the complement system at an earlier stage than eculizumab might be an important treatment strategy for patients with PNH, especially those who do not respond well to eculizumab.
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