Using minimal Factor H therapy and normothermic conditions to prepare kidneys for transplantation

Kidney transplant is the gold-standard treatment for patients with renal failure. However, the supply of organs is limited in number and quality. This has necessitated the transplantation of kidneys from donation after the donors death or from non-optimal donors that are associated with increased risks. These kidneys are associated with prolonged times without adequate oxygen supply and increased cellular damage resulting in increased organ injury immediately after transplant. This can shorten the long-term survival of the kidney and result in patients requiring another transplant, compounding the organ shortage crisis.
We have developed a novel anti-complement therapy based on a blood defence protein called factor H and one of its related proteins. Our drug is called HDM-FH (homodimeric minimal factor H). HDM-FH has been found to be highly effective in experimental rodent models of kidney disease. HDM-FH should have a clear use in transplantation. The complement system normally protects against invading pathogens and helps to clear cellular waste in our bodies. However, complement can become over active and it drives inflammation. In transplantation, the transplanted organ can be detected as non-self (like a pathogen) and activation of complement can lead to organ rejection. This rejection can be immediate or can take years due to complex processes that are triggered by the complement activation.
Thus, preventing complement activation and associated cellular/organ injury during the first minutes of transplantation will significantly prolong the survival of transplanted organ and the well being of the transplant recipient.
In Newcastle, we are working on methods to improve the function of kidney through a technique call ex vivo normothermic machine perfusion (EVNP for short), i.e. organs destined for transplant are warmed up with oxygenated blood flow in the lab and allowed to recover from the shock of being transported between hospitals (in cold liquids with no oxygen) prior to organ transplant. EVNP has shown promise in the re-conditioning of organs that might otherwise have been deemed unfit for transplant. Our plan is to try to further improve the outcome of transplanted organs after EVNP by using this system to introduce our anti-complement drug to the kidney, where it can bind and wait until the organ is transplanted into the recipient. Upon transplant, HDM-FH will then act as an organ defence against the recipients immune system.

In this study, we will model exposure of human (discarded human kidneys - deemed unfit for transplant by transplant surgeons) and pig kidney (similar size etc to human, readily available from farm production) to the drug and assess how well it remains bound to the organ during EVNP. We will then model, by using whole blood in the EVNP system in the lab, whether we can show complement activation on the organ and that our drug can reverse that. After the successful completion of these experiments, we would use EVNP of pig kidney and transplantation into a small number of pigs (up to 12) to test our drugs in as robust a fashion as possible. These pig transplant experiments (in conjunction with existing data on pig kidney EVNP) would provide important evidence of the ability of our anti-complement drug to protect kidney in a whole animal system. We will be able to assess safety of the drug and any unexpected events with its use. These studies would guide us in the steps to testing these drugs in human transplant studies. Additionally, the success of these drugs in protecting kidneys from complement could lead to the use of the drugs in other situations where complement needs to be controlled, such as the rare kidney disease, C3G.

Overall, this research is designed to lead to better organ transplant success, even from organs which are considered borderline for transplant. It will eventually be of significant benefit to the many thousands of people waiting on a renal transplant.

Factor H (FH) is the key fluid phase regulator of Complement. We developed a homodimerised mini-FH (HDM-FH) drug that is significantly more active than full-length FH. We recently demonstrated that the HDM-FH drug will home to the mouse kidney (FH deficient mice) and reverses uncontrolled complement activation, establishing the functionality of HDM-FH in vivo (JASN, 2018). Therefore, we postulate that HDM-FH may offer an exciting potential to restrict complement activation and associated kidney damage during reperfusion of kidneys after organ transplantation. Indeed, we have developed some preliminary data in vitro that supports that hypothesis.
In order to test this idea more fully, we will develop unique model systems in Newcastle, based on our extensive knowledge of ex vivo normothermic machine perfusion (EVNP). We will first confirm our pilot binding data of HDM-FH to human kidney, we will next introduce whole blood into the system to re-create the effects of reperfusion injury and establish a novel ex vivo model system. We will carry this out in both human and porcine kidney, paving the way to test the drug in vivo. In order to achieve this we will develop a porcine version of the HDM-FH construct and fully test its functionality in our standard tests (see JASN, 2018) in parallel to developing the complement activation model. This drug will then be tested in pig kidney EVNP. We will continue to evaluate the use of the original human HDM-FH to bind and protect discarded human kidneys from complement activation while on the EVNP rig, assessing efficacy and toxicity of the drug ex vivo. Once these have all been concluded successfully, we would carry out pig auto-transplant studies, where donor organs are coated with HDM-FH on the rig and then transplanted back into the donor pig. These animals would be monitored for 10 days to follow animal health and organs collected for in depth histology. These studies would provide proof of concept for human trials

Who will benefit?
Every year 2 million people die world wide due to lack of access to kidneys for transplant. The role of complement in ischemia reperfusion injury and failure of renal transplants is clear. Therefore, the successful completion of our study will pave the way to a new approach to help optimally condition organs for transplant, which will quickly lead to more organ availability for patients requiring transplant. The findings will be most relevant to renal transplant clinicians but may be of value to all clinicians carrying out large organ transplant. The ability to perform reliable, insightful pre-clinical tests on complement-suppressing molecules in whole organs, and whole blood systems, in normothermic conditions will be a great leap forward for pharmaceutical companies and researchers alike. It will provide a unique and much needed model system to test immuno-modulatory drugs and beyond. It will expedite the development of anti-complement and anti-ischemic injury therapeutics which will directly benefit patients, their relatives and carers.

How will they benefit?
1. This study will lead directly to methods which reduce the incidence of delayed graft function in renal transplant. By doing so, all renal transplant patients will benefit from reduced time in hospital, reduced waiting times on transplant lists, reduced complications and arguably, most importantly, a marked increase in the long-term function of their graft. This would benefit patients and the healthcare system enormously.

2. The development of new ex vivo model systems with whole blood and active complement will provide a unique tool to evaluate strategies to reduce ischemic reperfusion injury beyond the use of single therapy. These system will allow safety testing of a large majority of therapeutic approaches without risk to patients in the outset. Dosing strategies and toxicology evaluations are all feasible. Thus, drugs can rapidly be tested and the most promising rapidly progressed to large animal tests or clinical trials as appropriate. This will save the company and or tax payer millions in failed approaches. The ability to carry out realistic evaluation of agents and fully triage drugs will benefit everyone involved in this type of research as well as the patients who will gain the best treatment available in the most timely fashion.

3. Improving quality of life for patients inflicted by deregulated complement activation is a major strategic goal and therefore clinical validation of the HDM-FH drug would bring that a step closer. Complement maintains homeostasis as well as fighting infections. Complement malfunctions increase with age, for example the largest single risk factor of susceptibility to age-related macular degeneration are linked to polymorphisms in complement proteins that control C3 activation; there is the link between Alzhemier's disease and variants in the genes for clusterin and complement receptor-type 1. The HDM-FH drug we are developing and testing herein could not only be used in transplantation but may an important treatment option for C3G patients, IgA nephropathy patients or indeed, any patient where complement over activity or imbalance is well appreciated.