Worldwide first finalized study of preclinical life-supporting orthotopic pig-to-baboon cardiac xenotransplantation (XT): Constant reproducible 3-months-survival up to half a year meets the ISHLT guidelines for first clinical trials
Paolo Brenner1,3, Bruno Reichart3, Matthias Längin2,3, Tanja Mayr3, Sonja Guethoff3, Stefan Buchholz1, Sebastian Michel1, Isabelle Lutzmann3, Fabian Werner3, Lara Issl3, Jiawei Ying3, Ann Kathrin Fresch1, Maren Mokelke1, Julia Radan1, Ines Buttgereit1, Andreas Bauer2, Nikolai Klymiuk4, Walter Hermanns6, Keith Reimann5, David Ayares7, Christian Hagl1, Stig Steen8, Eckhard Wolf4, Jan-Michael Abicht2,3.
1Dept. of Cardiac Surgery, Clic of Grosshadern, University of Munch (LMU), Munich, Germany; 2Dept. of Anaesthesiology, Clic of Grosshadern, University of Munch (LMU), Munich, Germany; 3Walter-Brendel-Centre, University of Munich (LMU), Munich, Germany; 4Dept. of Molecular Animal Breeding and Biotechnology, University of Munich (LMU), Munich, Germany; 5MassBiologics, University of Massachusetts Medical School, Boston, MA, United States; 6Department of Veterinary Pathology, University of Munich (LMU), Munich, Germany; 7Revivicor , Inc., Blackburg, VA, United States; 8Department of Cardiothoracic Surgery, University of Lund, Lund, Sweden
Introduction: According to the guidelines and recommendations of the ISHLT advisory board a 90-days-survival of at least 60% in a life-supporting orthotopic pig-to-baboon model (oXHTx) is necessary to begin first clinical cardiac XT studies. We started to reproduced a brilliant survival of transgenic pig hearts up to 3 years in a non-life-supporting heterotopic abdominal model ((1) Mohiuddin et al., Nat. Commun. 2016;7,11138) in our life-supporting orthotopic model with nearly the same immunosuppression (IS) dominated by a CD40mAb costimulation blockade. Another problem specific for oXHTx like the early perioperative cardiac xenograft dysfunction (PCXD, caused by ischemic crystalloid cardioplegia) and cardiac xenograft overgrowth (caused by the quick physiological pig heart growth and hypertrophy) were prevented by using a new non-ischemic cold perfusion and preservation technique and a p.o. growth inhibition by an antihypertensive and anti-proliferative drug therapy.
Methods: In this group 8 GalKO/hCD46/hTM transgenic (tg) pig hearts were transplanted orthotopically in baboons. Basic IS consisting of ATG, rituximab, mycophenolate, cortisone and 50 mg/kg CD40mAb (mouse/rhesus-Ab). To prevent PCXD as an early cardiac low output and “stunning myocardium”, instead of crystalloid Bretschneider cardioplegia we used a hyperoncotic, non-ischemic 8oC cold perfusion solution with oxygenated erythrocytes and albumin. To inhibit pig xenograft overgrowth and hypertrophy, antihypertensive drugs (enalapril, metoprolol) and an intravenous mTOR inhibitor (temsirolimus) as anti-proliferative drugs were administered.
Results: In contrast to a previous group with Bretschneider cardioplegia (Längin et al. Nature 2018;564:430-433 (2)) now with non-ischemic cold perfusion technique no PCXD occurred, stroke-work-index was high and catecholamines low. Two baboons with pCMV-positive donor hearts died of infections on day 14 (pancreatitis) and on day 26 (kidney failure). Using the therapies against xenograft (over)growth and hypertrophic diastolic heart failure, now all other 6 recipient baboons achieved long-term survival and 4 had to be actively terminated after 90 days with a well beating xenograft (according to the allowance of our government) and 2 experiments could be extended up to half a year (182 and 195 days). Immunologically no hyperacute or delayed rejection was observed. All baboons were in excellent physical conditions with normal parameters in hematology and clinical chemistry the whole period.
Conclusion: After 25 years of intensive experimental research in oXHT of multi-tg pig hearts since 2017 a major progress and with this group the essential breakthrough occured demonstrating a consistent reproducible long-term survival up to 3 (n=4) and 6 months (n=2). This meets the prerequisite according to the ISHLT guidelines before starting a clinical phase I study with 10 patients (as bridge-to-allotransplantation or destination therapy) in the next 2 to 3 years.
[1] (1) Mohiuddin, MM, Singh AK, Corcoran PC, Thomas Iii ML, Clark T, Lewis BG, Hoyt RF, Eckhaus M, Pierson Iii RN, Belli AJ, Wolf E, Klymiuk N, Phelps C, Reimann KA, Ayares D, Horvath KA. Chimeric 2C10R4 anti-CD40 antibody therapy is critical for long-term survival of GTKO.hCD46.hTBM pig-to-primate cardiac xenograft. Nat. Commun. 2016;7,11138.
[2] Längin M*, Mayr T*, Reichart B, Michel S, Buchholz S, Guethoff S, Dashkevic A, Baehr A, Egerer S, Bauer A, Mihalj M, Panelli A, Issl L, Ying J, Fresch AK, Buttgereit I, Mokelke M, Radan J, Werner F, Lutzmann I, Steen S, Sjöberg T, Paskevicius A, Qiuming L, Sfriso R, Rieben R, Dahlhoff M, Kessler B, Kemter E, Klett K, Hinkel R, Kupatt C, Falkenau A, Reu S, Ellgass R, Herzog R, Binder U, Wich G, Skerra A, Ayares D, Kind A, Schönmann U, Kaup FJ, Hagl C, Wolf E, Klymiuk N, Brenner P* & Abicht JM* (* = equal). Consistent success in life-supporting porcine cardiac xenotransplantation. Nature. 2018;564:430-433.
