title: Preclinical safety, pharmacokinetics, pharmacodynamics, and biodistribution studies with Ad35K++ protein: a novel rituximab cotherapeutic.
abstract: Rituximab is a mouse/human chimeric monoclonal antibody targeted toward CD20. It is efficient as first-line therapy of CD20-positive B-cell malignancies. However, a large fraction of treated patients relapse with rituximab-resistant disease. So far, only modest progress has been made in treatment options for rituximab refractory patients. One of the mechanisms for rituximab resistance involves the upregulation of CD46, which is a key cell surface protein that blocks the activation of complement. We have recently developed a technology that depletes CD46 from the cell surface and thereby sensitizes tumor cells to complement-dependent cytotoxicity. This technology is based on a small recombinant protein, Ad35K++ that binds with high affinity to CD46. In preliminary studies using a 6 × histidinyl tagged protein, we had demonstrated that intravenous Ad35K++ injection in combination with rituximab was safe and increased rituximab-mediated killing of CD20-positive target cells in mice and nonhuman primates (NHPs). The presence of the tag, while allowing for easy purification by Ni-NTA chromatography, has the potential to increase the immunogenicity of the recombinant protein. For clinical application, we therefore developed an Ad35K++ protein without His-tag. In the present study, we performed preclinical studies in two animal species (mice and NHPs) with this protein demonstrating its safety and efficacy. These studies estimated the Ad35K++ dose range and treatment regimen to be used in patients. Furthermore, we showed that intravenous Ad35K++ injection triggers the shedding of the CD46 extracellular domain in xenograft mouse tumor models and in macaques. Shed serum CD46 can be measured in the serum and can potentially be used as a pharmacodynamic marker for monitoring Ad35K++ activity in patient undergoing treatment with this agent. These studies create the basis for an investigational new drug application for the use of Ad35K++ in combination with rituximab in the treatment of patients with B-cell malignancies.
authors.affiliation: Division of Medical Genetics, University of Washington , Seattle, Washington, USA.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Richter
authors.affiliation: Division of Medical Genetics, University of Washington , Seattle, Washington, USA.
authors.forename: Roma
authors.initials: R
authors.lastname: Yumul
authors.affiliation: Division of Medical Genetics, University of Washington , Seattle, Washington, USA.
authors.forename: Kamola
authors.initials: K
authors.lastname: Saydaminova
authors.affiliation: Division of Medical Genetics, University of Washington , Seattle, Washington, USA.
authors.forename: Hongjie
authors.initials: H
authors.lastname: Wang
authors.affiliation: Washington National Primate Research Center , Seattle, Washington, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Gough
authors.affiliation: Washington National Primate Research Center , Seattle, Washington, USA.
authors.forename: Audrey
authors.initials: A
authors.lastname: Baldessari
authors.affiliation: Mayo Clinic , Rochester, Minnesota, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Cattaneo
authors.affiliation: BRIM Biotechnology, Inc , Taipei, Taiwan.
authors.forename: Frank
authors.initials: F
authors.lastname: Lee
authors.affiliation: BRIM Biotechnology, Inc , Taipei, Taiwan.
authors.forename: Chung-Huei Katherine
authors.initials: CH
authors.lastname: Wang
authors.affiliation: BRIM Biotechnology, Inc , Taipei, Taiwan.
authors.forename: Haishan
authors.initials: H
authors.lastname: Jang
authors.affiliation: University of Edinburgh , Edinburgh, UK.
authors.forename: Anne
authors.initials: A
authors.lastname: Astier
authors.affiliation: Division of Medical Oncology and Fred Hutchinson Cancer Research Center, University of Washington , Seattle, Washington, USA.
authors.forename: Ajay
authors.initials: A
authors.lastname: Gopal
authors.affiliation: Compliment Corp., Seattle, Washington, USA; PAI Life Sciences Inc., Seattle, Washington, USA.
authors.forename: Darrick
authors.initials: D
authors.lastname: Carter
authors.affiliation: Division of Medical Genetics, University of Washington, Seattle, Washington, USA; Compliment Corp., Seattle, Washington, USA; Department of Pathology, University of Washington, Seattle, Washington, USA.
authors.forename: André
authors.initials: A
authors.lastname: Lieber