September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
COMPLEMENT FACTOR I BIOACTIVITY: A POTENTIAL BIOMARKER FOR ANTI-AMYLOID BETA TREATMENT IN AGE-RELATED MACULAR DEGENERATION/GEOGRAPHIC ATROPHY
Author Affiliations & Notes
  • Francisco J Lopez
    GSK, King of Prussia, Pennsylvania, United States
  • Hong Chen
    Alliance Pharma, Malvern, Pennsylvania, United States
  • Yong-Qing Lin
    Alliance Pharma, Malvern, Pennsylvania, United States
  • Sanjay Kumar
    GSK, King of Prussia, Pennsylvania, United States
  • Megan M McLaughlin
    GSK, King of Prussia, Pennsylvania, United States
  • Footnotes
    Commercial Relationships   Francisco Lopez, Allergan (E), GSK (E); Hong Chen, Alliance Pharma (E); Yong-Qing Lin, Alliance Pharma (E); Sanjay Kumar, GSK (E); Megan McLaughlin, GSK (E)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 2129. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to Subscribers Only
      Sign In or Create an Account ×
    • Get Citation

      Francisco J Lopez, Hong Chen, Yong-Qing Lin, Sanjay Kumar, Megan M McLaughlin; COMPLEMENT FACTOR I BIOACTIVITY: A POTENTIAL BIOMARKER FOR ANTI-AMYLOID BETA TREATMENT IN AGE-RELATED MACULAR DEGENERATION/GEOGRAPHIC ATROPHY. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2129.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract

Purpose : Complement activation, particularly the alternative pathway, is thought to be central to the pathogenesis of age-related macular degeneration (AMD). Amyloid β (BAM) is one of the components of drusen, a hall mark of AMD, and complement activation by BAM through interaction with complement factor I (CFI) has been proposed. CFI, a serine protease, limits C3 convertase formation in the alternative pathway through its actions on C3b. An anti-BAM monoclonal antibody (mAb), therefore, is expected to overcome the BAM-mediated reduction of CFI activity. Our goal was to establish a quantitative assay to measure CFI bioactivity and the effect of an anti-BAM mAb, for use not only as a biomarker for target engagement and effectiveness of anti-BAM therapy, but also as a bioassay during the mAb’s manufacturing.

Methods : We have established an in vitro cofactor assay that uses ELISA to quantify iC3b production. Additionally, a modified protocol allows for the measurement of the plasma volume needed to convert half of the C3b added in the reaction mix into iC3b (which is defined as 1 mU of CFI activity in the assay). The estimated volume, therefore, indicates the potency of sample CFI for cleaving C3b. By measuring the concentration of CFI protein by ELISA, the specific activity of the protein can be readily determined.

Results : Our studies show that pre-incubation of CFI with BAM significantly reduces the ability of CFI to cleave C3b into iC3b, recapitulating previous studies. BAM-mediated reduction of CFI activity can be blocked by GSK933776, an anti-BAM mAb, which is directed against the N-terminus of BAM. These data provide proof-of-principle for this assay. In addition the assay has been modified to measure CFI bioactivity in plasma samples.

Conclusions : Our data support assays that may provide early evidence of therapeutic benefit for anti-BAM therapies in long AMD/GA clinical trials if BAM-mediated inhibition of CFI bioactivity plays a role in AMD. In addition, these assays are potentially useful to evaluate anti-BAM monoclonal antibody potency during manufacturing and release.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×