Monoclonal antibodies targeting novel sites of vulnerability in marburg virus glycoprotein

Filoviruses, consisting of two major virus families including the ebolaviruses and marburgviruses (MARV and
RAVV), cause periodic outbreaks of severe viral hemorrhagic fever with mortality rates as high as 90%. Since it
is difficult to predict the species that would dominate future outbreaks, development of broadly protective
therapeutics to prevent and manage future filovirus outbreaks is of high priority. In sharp contrast to the recent
major breakthrough reported by us and others on isolation and development of a number of effective and broadly
neutralizing mAbs (bNAbs) for ebolaviruses, only a single class of mAbs against marburgvirus GP has been
described that target the same epitope within the receptor binding site (RBS) of MARV and RAVV GP. MR191
is the only MARV/RAVV GP RBS-specific monoclonal antibody (mAb) that has been shown to protect against
MARV infection in nonhuman primates (NHPs) however at very high doses (2 doses of 50 mg/kg each). Thus, it
is important to identify novel sites of vulnerability in MARV/RAVV GP and develop more potent
immunotherapeutics against these deadly viruses. Having a variety of bNAbs will allow the design of therapeutic
cocktails containing multiple mAbs targeting distinct epitopes, a strategy that has been shown tobe extremely
effective against ebolaviruses to combat possible virus escape variants.
There has been a long-standing and productive collaboration between Integrated BioTherapeutics (IBT) and
University of Maryland (UMD) that has recently resulted in highly potent ebolavirus bNAbs with remarkable
efficacy in animal models including nonhuman primate (NHP) and ferret models of EBOV, SUDV, and BDBV
infection (Zhao et al., Cell 169, 891-904 e815 (2017)). Lately, using a prime/boost immunization strategy in NHPs
combined with a novel memory B cell counter-screening with engineered GP mutants, we were able to isolate,
for the first time, a group of highly potent MARV/RAVV bNAbs that target a new class of epitopes distinct from
the RBS-binding MR series. In this STTR application, we aim to address the major challenge of MARV
immunotherapy by developing top lead candidate marburgvirus therapeutic antibodies derived from these novel
MARV/RAVV bNAbs. We will i) select 3-4 lead therapeutic mAbs among the current bNAb candidates; ii) optimize
the lead mAbs and select for the final humanized/optimized candidate by state-of-the-art computer-aided
optimization and efficacy study in a stringent guinea pig model of MARV infection; and iii) identify the final lead
mAb (or cocktail) by testing the efficacy of candidates in NHP model of MARV infection. Upon completion of the
proposed Phase I project we envision a Phase II project with the following objectives: i) expand the efficacy
studies to RAVV and dose optimization in NHPs; ii) develop manufacturing cell lines in CHO cells, iii) develop
bioanalytical methods for product release and PK, and iv) conduct safety and tissue cross reactivity studies using
the GLP-grade clinical candidate. If successful, we anticipate further development of the product under DoD or
BARDA funding and approval under FDA Animal Rule.Filoviruses are among the deadliest pathogens known to humans. The Ebola virus disease outbreak in West
Africa (2014-2016), caused by the Zaire Ebola virus, resulted in over 28,000 cases and 11,000 deaths. In addition
to Ebola virus, a related filovirus called Marburg has caused five outbreaks in the past 10 years with high fatality
rates. This proposal is aimed at developing effective immunotherapeutics against Marburg virus. We have
generated several antibody drug candidates that protect against Marburg infection. Under this proposal we will
further characterize these drug candidates and test their efficacy in mice and nonhuman primates. This study, if
successful, will set the stage for clinical development of an effective therapeutic for human use.