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Op-Ed: Professor Mark Cragg speaks to News-Medical about his research which involves turning autoimmunity drugs into anti-cancer treatments.
I am interested in immunotherapy, using the immune system to treat disease, and often cancer and autoimmunity are the opposite sides of the coin, one side where the immune system is suppressed and the other where it is too active.
Understanding one typically helps to understand the other.
There are many varied treatments ranging from steroids, chemotherapy, small molecule targeted drugs as well as biologics such as antibodies, which is my main focus.
CD40 is a receptor expressed on the cell surface of several immune cell types, known as antigen-presenting cells (APC) such as B cells and dendritic cells.
It is a member of the Tumor Necrosis Factor Receptor Super-Family (TNFRSF) and is essential for the initiation and regulation of adaptive immunity.
The interaction between CD40 and its endogenous ligand CD40L is critical for mounting an effective immune response against exogenous pathogens and naturally arising tumors.
CD40 over-stimulation is implicated in various autoimmune syndromes such as lupus and colitis as well as transplant rejection, driving B cell and T cell stimulation leading to inappropriate activation, and tissue destruction.
In contrast, CD40 under-stimulation reduces the activation of the APCs and reduces the generation and expansion of CD8+ T cells that control tumors.
The drugs used in autoimmunity are designed to block the interaction between CD40 and its ligand (CD40 ligand; CD40L). This prevents immune signaling in the APC, reducing immune activation.
We did not develop this antibody – it had already been developed and used in the clinic to treat autoimmunity.
We simply used the V region sequences to make a series of modified antibodies that differed in their Fc domains – displaying human IgG1, 2, or 4 isotypes.
We then explored how these antibodies modified immune responses, showing that the hIgG1 and 4 antibodies reduced immune stimulation whereas the hIgG2 antibody did the opposite and boosted the immune responses.
We learned how transformative just changing the Fc domain can be for the function of the antibody; converting a “blocking” antibody into a super-active one.
We also highlighted this property of the hIgG2 isotype is FcgR-independent and is related to its unique hinge region which allows disulfide shuffling.
The converted antagonist showed curative antitumor synergy with cell therapy and vaccination strategies.
Firstly, it was more active at stimulating immune responses in our various assays than the current most active antibody available in the clinic. Moreover, we think the really exciting thing is that it does not require interaction with Fc receptors for its activity whereas other antibodies do.
Fc receptor expression is variable in different people and different tumors which may explain why some people do or do not respond to these drugs.
By generating an antibody-drug that does not require Fc receptors, we hope to be able to get strong responses in more patients.
We hope that this drug and others like it could help pave the way for more effective treatments.
We hope that this research could potentially apply to vaccination, as we can also boost antibody responses to foreign antigens with this drug.
First, more extensive experiments to assess how best to deliver the drug. Then, we need to perform the usual early human studies, first assessing safety and finding a safe and effective dose before it can progress to use in patients.
We are really interested in WHY this antibody is so active.
What does it do to the receptor? How does it cluster? Is the signaling it evokes qualitatively or quantitatively different?