The present invention relates to methods of evaluating and treating organs during isolated organ perfusion, and kits for carrying out this analysis.

Background to the Invention

Organs that can be transplanted from one person or animal to another include the heart, kidneys, liver, lungs, pancreas and bowels. Kidney transplants are most commonly performed. Transplants of the heart, liver and lungs are also regularly carried out. However, there are many more people in need of organ transplants than organs available and, tragically, many people die while waiting for a suitable organ.

It is very important that organs are kept in the best possible condition between harvesting and transplantation. In order to maintain the organ in the best possible condition, the organ can be isolated from the blood circulation of the donor, and perfused with a Perfusate. For example, ex vivo lung perfusion (EVLP) is today considered a safe procedure with the capacity to increase the number of lungs available for transplantation. More than 350 transplantations have been performed after EVLP. However, the procedure is only carried out at a few lung transplantation centers around the world.

In order to have more available lungs to save more patients with terminal lung diseases, the technique needs to be adopted by more centers. However, one of the current difficulties is that methods for evaluating an organ to determine whether or not it is suitable for transplantation are not very advanced. Wider adoption of this technique would be more likely if objective data was available to determine whether or not to use the organ for transplantation.

An isolated organ perfusion procedure today involves removing an organ such as a lung or lungs from a donor and connecting it to a perfusion circuit, comprising a pump(s), a reservoir, a heater cooler, an oxygenator and a ventilator. If the organ is another organ than a lung, a ventilator is not used. The vasculature of the organ is pumped with a Perfusate. The Perfusate might be, for example, STEEN Solution (see WO2002/035929) or another solution appropriate for organ perfusion. The solution might contain erythrocytes and it might be oxygenated. EVLP is only one form of isolated organ perfusion. Furthermore an organ can be circulatorily isolated while remaining within the body in an in vivo lung perfusion (IVLP).

Different lung specific parameters can be evaluated during the perfusion but to date these have mainly been physical parameters. For example, parameters such as pulmonary vascular resistance (PVR), compliance and oxygenation capacity have been monitored. While these parameters provide some information to the user, they do not give definitive information about whether or not an organ should be selected for transplant and so the decision to transplant or not is still largely based on subjective evaluation. Therefore there is an urgent need for additional objective parameters that could be used to determine the quality of an organ during an organ perfusion evaluation.

The focus on molecular biomarkers in the literature has been related to interleukin signalling, especially IL-Ιβ, IL.6, IL-8, IL-10 and TNFa. However despite several publications these markers have not been shown to be useful in a clinical setting. One reason being that they are generally not analyzed with point-of-care (PoC) methods and therefore the information, even if clinically valuable, is not available to the Clinicians when the decision to transplant or not has to be made. An EVLP procedure normally lasts between 2 and 6 hours, and information not available in this time frame is of no use in informing the decision as to whether or not to transplant that organ.

Furthermore, Ischemia Reperfusion Injury (IRI) is a well-known complication to organ transplantation. It occurs at the time of recirculation of the organ with oxygenated blood. Although an acute phase reaction, the effects of this early injury are believed to be a significant contributor to later morbidity and mortality in the organ recipients. A better ability to select and de-select organs for transplantation could alleviate IRI and improve survival and health in the recipients both in short and long term. Summary of the Invention

According to a first aspect, the present invention relates to a method of evaluating lung/lungs during isolated organ perfusion, the method comprising the steps of: perfusing the isolated organ with a Perfusate; and measuring the concentration in the Perfusate of the bio marker Surfactant protein D (SpD).

According to a fourth aspect the present invention relates to a kit for analysis of a Perfusate during isolated lung perfusion, the kit comprising an immunologic analysis for SpD. Accordingly, the present invention provides a much needed method of evaluating an organ in an objective way by measuring the concentration in the Perfusate of the key biomarker SpD that can indicate the health of the organ. Further information about the biomarker is given below.

The isolated organ can be from an animal or a human being, and is a lung or lungs. . By isolated, we mean that the organ is isolated from the circulatory system. It can be isolated in vivo or isolated ex vivo as is already known in organ perfusion. It is then perfused with a Perfusate and the Perfusate can be analysed. Specifically, the concentration in the Perfusate of the biomarker SpD is measured. The present invention relates specifically to measuring SpD., A single measurement of the concentration of the SpD biomarker can be taken, but it is preferable that the concentration of the one or more biomarkers is measured continuously over a predetermined time period or repeatedly at predetermined intervals, this is preferably throughout the perfusion period which is usually between 1 and 6 hours.

In order to use the method for evaluating the organ in practice, the measured concentrations in the Perfusate of the SpD biomarker are compared against reference values, and the organ is then selected or deselected on the basis of how the measured concentrations compare with the reference values. This gives the clinician an objective parameter to use to determine whether or not the organ is suitable for transplantation. Additionally, the isolated organ can actually be treated according to how the measured concentrations of biomarker compare to reference values. If certain conditions are met, the isolated organ can be treated by adding a component to the Perfusate. Advantageously, the treatment effect of the component on the isolated organ can be monitored by further evaluation.

The present invention also relates to methods of treating an organ during isolated organ perfusion. As discussed below, it is highly probable that the organ has been subjected to stress, simply from the negative effects of brain death or from ceased circulation in a non-heart beating donor. Accordingly, the organ can be treated independently from evaluation. This has the advantage that treatment can commence immediately, and is usually used in conjunction with evaluation, i.e. treatment is prior to or during evaluation. The overarching aim of the present invention is to improve the success rate of transplants, in order to improve quality of life for patients. Another overarching aim is to treat organs so that more organs can be successfully transplanted and more people can benefit from organ transplants. The organs are generally transplanted into another person, and are not transplanted back into the donor. Description

A peculiarity with isolated organ perfusion and even more so with isolated organ perfusion using a defined solution such as STEEN Solution as the Perfusate, is that no other organ systems are present. This provides a unique opportunity to investigate an organ system, but at the same time, the physiology is abrupt. Very little is actually known about how an isolated organ responds to its un-physio logical environment. It could be anticipated that the organ initiates its normal physiological reactions to for example inflammation and coagulation, but what happens when the organ is not receiving the external responses anticipated in an in vivo situation. This is a field of research that is largely unexplored. Perfusates are known to the skilled person such as STEEN solution. Any suitable Perfusate can be used in the present invention. Isolated organ perfusion is generally not done with a full blood Perfusate. One main reason for this is that blood contains several enzymatic systems that when activated could harm the organ. Examples of these systems are coagulation and complement activation. The organ has already been under stress in the donor and is more or less damaged from systemic effects of brain death or circulatory arrest. This existing damage could activate these enzymatic systems and further harm the organ. Immune cells present in whole blood are also particularly harmful during these circumstances. Therefore a solution like STEEN Solution, comprising physiological salts, dextran and albumin is considered safer for the organ. As none of the enzymatic systems nor any blood derived immune cells other than those resident within the organ are present, the organ is given a chance to heal and regain function during optimal conditions.

This relatively pure system, allows investigation of the molecular signalling done by the organ itself and immune cells that the organ is hosting, without disturbances from signalling from other sites.

Not only does this system provide an opportunity to evaluate the function of the organ, it also offers an opportunity to treat the organ. During isolated perfusion the organ can be treated with normal or elevated doses of pharmaceuticals or biologicals as no systemic side effects will occur.

Surfactant Protein D - Background

Surfactant protein D (SpD) is a water soluble protein with immune activity and function as opsonins on the epithelial/alveolar side of the lung.. SpD is a large multimer proteins.

It has been shown that SpD is reduced in Bronchio -Alveolar Lavage (BAL) samples from COPD patients, but that it was increased in blood samples, indicating a leakage (see Stockley 2014). It has not before been tested in the Perfusate during isolated organ perfusion.

Surfactant Protein D - In the Invention

Leakage of surfactant protein D (SpD) from the alveolar side to the vasculature could be viewed as a sign of disruption of the air-liquid barrier in the lung. The more pronounced this disruption is the worse is the function of the lung. Measuring SpD in the Perfusate of an isolated lung would therefore generate information about the lung function.

SpD could be analyzed for using for example immunologic assays. In any case the assay used should deliver results within about an hour or more preferably within 30 minutes to be useful during the actual procedure.

Reference values can be defined, where either a specific cut-off value for acceptable concentration of SpD could be used or the concentration could be followed over time during the isolated lung perfusion and the changes could be used to decide if the organ is well functioning or not and therefore whether it should be selected for transplantation and/or treatment and/or further evaluation. The analysis could be used on its own or in combination with other analysis. A combinatorial approach could improve sensitivity and/or specificity of the analysis as more organ functions are being tested.

For example the reference value could be a cut off level of SpD in the Perfusate of above 50 ng/ml, or above 80 ng/ml or above 100 ng/ml or about 120 ng/ml or above 130 ng/ml or about 140 ng/ml or about 150 ng/ml or above 160 ng/ml or above 180 ng/ml or above 200 ng/ml.

Above the reference values the organ would be deselected for transplantation. At or below the reference value the organ could be selected for transplantation, treatment and/or further monitoring.

SpD in the Perfusate

45 sets of human lungs were perfused ex vivo using STEEN Solution as the Perfusate. The perfusion was performed up to seven hours, although in most cases the perfusion was stopped after three or four hours, either to transplant the lung or to discard a lung that was not considered suitable for transplantation. The Perfusate was collected and frozen for subsequent immunologic analysis of SpD. Samples were normally collected at the beginning and then every hour. However, not all cases had samples collected at every time point. This was attributed to the clinical situation where the sample collection was to take place. Taking care of the organ was the primary task collection of samples necessarily came second.

When the data is aggregated it can be shown that discarded lungs have a higher increase of SpD then transplanted lungs. For each individual lung this is not always the case, and some transplanted lungs have values outside a suggested cut-off. Had the present invention been available, these lungs might have been deselected or preferably treated to become transplantable in relation to this parameter, if the analysis had been performed during EVLP. Such handling could have reduced IRI in the patient. Patient outcome data can be analysed to ensure that the reference values for organ selection, de-selection and treatment are optimised.

Table 5 - SpD measurements in ng/ml of Perfusate

accepted

22,13 103,01 accepted

44,29 29,11 accepted

22,74 0,00 35,47 accepted

94,07 79,59 56,01 accepted

0,00 35,38 32,23 accepted

8,88 28,19 60,64 accepted

0,00 13,25 31,91 88,97 accepted

22,85 54,10 43,77 accepted

169,99 262,33 288,53 293,31 accepted

7,19 57,10 87,94 79,86 90,52 120,30 accepted

71,07 121,40 164,29 172,92 170,82 accepted accepted

0,00 14,95 40,24 50,04 63,65 accepted

62,80 65,95 130,66 accepted

54,38 102,18 132,60 149,00 154,49 201,17 164,16 accepted9,65 12,69 29,07 30,15 45,22 55,47 accepted,00 0,00 0,00 11,25 52,12 accepted,00 108,60 167,75 210,42 224,94 accepted,00 71,83 168,38 182,22 189,97 accepted,00 0,00 33,37 44,28 56,54 86,76 accepted,00 0,00 25,04 24,13 53,46 51,32 76,27 76,27 accepted,00 73,09 123,46 203,03 236,11 245,20 263,22 accepted,00 0,00 0,00 0,00 16,53 accepted accepted,00 15,66 80,51 99,24 accepted accepted,00 0,00 11,39 18,80 accepted As values generally are increasing over time the increase rate or change could be an alternative measure of organ function or well-being. This ongoing increase could also be viewed as an opportunity to treat and to monitor the effect of the treatment.

A further correlation with clinical data would be used to optimize the cut-off levels. It is anticipated that the patients receiving the lungs with more values outside the ranges or cut offs did not do as well as patients receiving lungs with all values within the ranges or cut offs.