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A Novel Long-Acting Drug Conjugate for Extended Anti-VEGF Therapy

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Posterboard#: A0295

Abstract Number: 114 - A0295

AuthorBlock: Wesley M. Jackson1, Livia W. Brier1, Amy Twite1, Mavish Mahomed1, Ricardo Lamy2, Matilda F. Chan2
1Valitor, Inc., Berkeley, California, United States; 2Ophthalmology, UCSF, San Francisco, California, United States;

DisclosureBlock: Wesley M. Jackson, Valitor Code I (Personal Financial Interest), Valitor Code E (Employment), Valitor Code P (Patent), Livia W. Brier, Valitor Code I (Personal Financial Interest), Valitor Code E (Employment), Amy Twite, Valitor Code I (Personal Financial Interest), Valitor Code E (Employment), Mavish Mahomed, Valitor Code I (Personal Financial Interest), Ricardo Lamy, Valitor Code F (Financial Support), Matilda F. Chan, Valitor Code F (Financial Support)

Purpose
Anti-VEGF therapy is critical for treatment of wet AMD and other retinal neovascular diseases, and current anti-VEGF drugs require administration by intravitreal injection every 1-3 months. We have previously shown how a drug consisting of multiple copies (i.e., valency) of anti-VEGF proteins conjugated to single-chain hyaluronic acid (HyA) biopolymers can substantially extend its intravitreal half-life. In this project, we tested the binding affinity of a novel anti-VEGF antibody and verified its compatibility with the multivalent conjugation technology.

Methods
We obtained a novel single-domain (VHH) antibody using phage display against anti-VEGF A121. Antibody affinity maturation was performed by subsequent yeast against the same antigen. Finally, we expressed and purified the VHH with the highest Anti-VEGF binding affinity. Using published methods, we conjugated 30-50 the anti-VEGF VHH to HyA (~800 kDa) and measured their VEGF-A binding affinity using biolayer interferometry. For comparison, we also generated multivalent conjugates using anti-VEGF designed ankyrin repeat proteins (DARPins) and single-chain antibodies (scFv). We measured the intravitreal half-lives of multivalent anti-VEGF conjugates using a rabbit model. In each eye, we injected 50 μL of a fluorescently tagged protein (600 μg/mL), either unconjugated or as a multivalent conjugate. At various times after injection, we measured the concentration of the anti-VEGF protein in the vitreous and the retina by fluorescence imaging (PerkinElmer IVIS) and/or mass spectrometry. We fit the intravitreal concentrations to exponential curves to determine the half-life of each treatment.

Results
The novel anti-VEGF VHH obtained via phage display and affinity maturation exhibited high binding affinity to VEGF-A, which was comparable to existing anti-VEGF drugs. In the rabbit model, the intravitreal half-life of the multivalent anti-VEGF VHH conjugates was also equivalent to our previous findings (i.e., up to 6-fold longer than the corresponding unconjugated anti-VEGF protein: p<0.005, t-tests).

Conclusions
Multivalent protein conjugation is an effective strategy to enable less frequent administration of anti-VEGF therapy. Multivalent anti-VEGF VHH conjugates exhibited slower intravitreal diffusivity and no reduction in bioactivity. Therefore, we have validated the use of a novel anti-VEGF VHH antibody for use with this technology.

Layman Abstract (optional): Provide a 50-200 word description of your work that non-scientists can understand. Describe the big picture and the implications of your findings, not the study itself and the associated details.
Anti-VEGF drugs are used to preserve visual acuity for patients with a variety of ophthalmologic diseases. However, effective treatment using these drugs requires that the patients receive an injection into their eye to administer the drug, typically at 4-12 week intervals. We are developing a modified version of these drugs that will remain in the eye for a substantially longer interval, and we hope to reduce the number of injections required for effective treatment to just two per year.