#projectEBOLA is FUNDED

 

THANK YOU BACKERS... We reached our goal early and we all made the news today: Potential ebola treatment finds backers in crowd-funded campaign, SFBizTimes!

Whew, I must admit there was a moment in the 2nd week where funding hit a wall and I started to question the viability of the campaign. It was unexpected given the extensive media coverage in the first week. Some people complained about the hassle of having to register in order to donate which I can relate to. Perhaps the negative press from the SF Chronicle hurt us? Maybe people were just ignoring ebola or thinking institutions and foundations would surely step in and help out (NOPE!)? But final week social media coverage was the push we needed to encourage the final few backers to donate and just squeak it over the edge. (That, and fronting $5K from OncoSynergy, of course, in matching funds.)

In any case, I am in active communication with the labs that will perform the initial experiments and hopeful they can get started this week in parallel. In addition, there are some BSL-2 studies that we will do in-house as further support of our hypothesis. But let's take a step back...

SCIENTIFIC RATIONALE. I have been quite busy with the cancer side of OncoSynergy so, until now, I have not been able to expand upon the scientific rationale behind our approach using our anti-CD29 antibody, OS2966, to treat ebola virus disease (EVD). I hope to shed some additional light on this here now.

First, I want to say that I generally credit the success of my scientific pursuits to my undergraduate developmental neurobiology professor, Dr. Marti Bosma, PhD. She ingrained in me the mantra for demonstrating a particular molecule or pathway is involved in a biological process: 1) it is expressed in the right place, 2) it is expressed at the right time, 3) you can model it in vitro (in a petri dish), 4) you can block it in vivo (in an animal model or human). Of all requirements, I feel the first is the most important (in combination with clinical natural history). So, my approach to all hypotheses always begins with histology/histopathology from human or a relevant animal model where cells are in the proper context (i.e., NOT on a plastic dish). This is because, by manipulating cells in vitro it is possible to derive results that are not found in whole organisms/nature. However, in vivo models have their limitations as well as we have seen in oncology.

Without further rambling, here is my calculus for treating EVD with OS2966:

CD29 IS EXPRESSED IN RIGHT PLACE

• Ebola is characterized by hemorrhagic fever. Although most organ systems are affected, this suggests particular tropism of ebola for blood vessels and the liver (the liver produces 6 clotting factors).
• CD29 is the major adhesion receptor in humans (beta1 integrin subunit). CD29 in adults is expressed in virtually all tissues, but particularly enriched in vascular endothelial (VE) cells which line the blood vessels (FIGURE 1A; VE cells would, of course, be the first to be exposed to virus in the blood-stream). CD29 also happens to be very highly expressed in the liver (FIGURE 1B).
• Notably, CD29 is not expressed in adult skeletal muscle or bone (FIGURE 1A). The only tissues not infected by ebola? ... skeletal muscle and bone!
• Other putative "ebola receptors" proposed in the literature including NPC1 (Miller et al, 2012) and TIM-1 (Kondratowitz et al, 2011) are puzzlingly NOT expressed in blood vessels. This doesn't mean they can't facilitate ebola infection in vitro. There are several steps to viral fusion where the different receptors can collaborate or function in series.
• Thus, the CD29 adhesion receptor is expressed in the right tissues consistent with the tropism and pathophysiology (Yang et al, 2000) of ebola. [Notably, other viruses exploit CD29-containing integrins as well including HHV-8 (Nemerow & Cheresh, 2002) and Adeno-Associated Virus Type 2 (Asokan et al, 2006).]

 

 

FIGURE 1. CD29 immunohistochemistry. (A, left), skeletal muscle section demonstrates positive CD29 staining (brown) only in endothelial cells of the vasculature between muscle bundles (purple). (B, right), CD29 (brown) is highly expressed in endothelial cells and hepatocytes of the liver.

CD29 IS EXPRESSED AT THE RIGHT TIME

• The White Lab (Dube et al., 2008) demonstrated cells grown as adherent cultures were 4x more susceptible to ebola infection than the same cells grown in suspension culture. Although they did not specifically look at CD29 expression they imply the missing link by stating "beta1 integrins (CD29) are CENTRAL to cell adhesion and signaling for anchorage-dependent cell growth" in the conclusion.
• Indeed, their followup paper directly confirmed the correlation of ebola infectivity with levels of CD29 which they manipulated genetically in multiple cell models (Shornberg et al, 2009).
• Thus, CD29 is expressed at the right time consistent with patterns of ebola infection.

A ROLE FOR CD29 IN EBOLA INFECTION IN VITRO

• The glycoprotein of ebola (GP) interacts with CD29 receptors in the initial steps of infection. This interaction could be blocked either by manipulating the amounts of CD29 (Schornberg et al, 2009), blocking GP with purified integrins (Takada et al, 2000), or inhibiting CD29 with monoclonal antibodies (Takada et al, 2000).
•  Takada et al, (2000) demonstrated inhibition of ebola GP mediated infection was inhibited by CD29 antibodies targeted to the N-terminal residues (particularly the ligand binding domain, LBD), but not the C-terminus.
• Thus, CD29, through its interactions with the ebola GP, appears to be necessary for successful ebola infection.

BLOCKING CD29 IN VIVO

• No in vivo data currently exists testing this hypothesis.
• However, similar to the blocking antibody used in Takada et al., (2000), above, OS2966 also targets the N-terminus LBD.
• Thus, OS2966 has the potential for blocking the CD29/GP interaction and subsequent ebola infection.

So, that is the basic rationale for pursuing this approach in ebola. It all leads to the very simple hypothesis of the current project which we will be testing in the laboratory very shortly. Sound good? Too late if not, J/K.

How does OS2966 compare to the other ebola drugs and vaccines in development? Briefly, the vaccine approaches are fairly standard, however, this is primarily useful in the PREVENTATIVE setting. Most vaccines do not help patients who are already infected, although it is possible. Concerningly, Takada et al, (2001) showed that we can produce antibodies after ebola exposure that actually WORSEN/HASTEN the disease! The same may occur in vaccinated patients so this will be something to watch out for during the trials, of which there are at least 2.

The other approaches are therapeutics targeted against one of the 7 proteins that make up the ebola virus itself. For example, ZMAPP is the "secret serum" used in Liberia last month in Americans working for Samaritan's Purse. ZMAPP is a cocktail of 3 antibodies against the ebola GP. Canadian company, Tekmira, is currently testing TKM-ebola which is an siRNA approach to inhibit the ebola nucleoprotein (NP). These are both logical strategies (although I am not personally a fan of siRNA for therapy). However, because ebola, like most viruses, rapidly mutates... therapeutics directly targeting ebola proteins may be more susceptible to drug resistance. In contrast, OS2966 blocks a receptor on the human host. The hope is that viral mutations are potentially less likely to have a negative impact on effectiveness of OS2966, although this has not been tested.

IN CONCLUSION. I hope this primer has been helpful for your understanding of our therapeutic approach with OS2966 for ebola. One month ago I never would have imagined this program would be where it is now and I look forward to our further progress in the coming month. Hopefully, I'll have some real data to share in the next update.

Best,

wSc