More background for your question, showing how they're trying to cover the bases (see abstracts below). Getting pig to like primates is not easy, and, as I've said, I assign little or no value to XenoMune at this time. But, OTOH, would you continue to support this research if you were Novartis?
Does anyone else consider that AlloMune is a threat to the XenoMune partner?
Wish list for tomorrow morning, just before market open......
(1) BTRN issues a PR indicating that AlloMune has been effective in early testing and that there are ten human chimeras (out of ten attempts) out there that bear two-haplotype disparate kidneys and who are not taking immunosuppressive drugs.
(2) MEDI issues a press release saying that it has been secretly testing 507 in RA, Sjogren's and lupus phase II trials, and that it completely resolves all disease within 30 minutes of the first administration. FDA will accept phase II data for all indications, fast track.
(3) the MEDI release goes on to say that, unfortunately, repeat dosing is necessary every three months for life.
(4) Novartis issues a PR indicating that procedures developed at BTRN have allowed for the successful engraftment of porcine marrow in primates.
(5) BTRN issues a press release indicating that Sykes, using AlloMune, has 434 patients in remission for various hematologic malignancies for periods of 434-3,520 days.
(6) BTRN issues a PR indicating that a use patent has issued for anti-CD40L- and CTLA4Ig-mediated induction of human bone marrow chimeras, no further conditioning required. Novartis initiates tender offer for shares of BGEN.
Transplantation 1998 Jul 27;66(2):252-9
Function of porcine adhesion molecules in a human marrow
microenvironment.
Warrens AN, Simon AR, Theodore PR, Sachs DH, Sykes M
Bone Marrow Transplantation Section, Transplantation Biology Research Center, Massachusetts General Hospital, Harvard
Medical School, Boston 02129, USA.
BACKGROUND: One way to circumvent the need for chronic immunosuppression in solid organ xenografting may be to
induce donor-specific tolerance using bone marrow transplantation. If this approach is to succeed in the pig-to-human species
combination, pig marrow must be capable of maturing into relevant tolerance-inducing cells and replenishing itself in host human
marrow. One possible barrier is adhesion molecule incompatibility. We have studied the compatibility across the pig-human
species barrier of two well-characterized ligands known to be important in hematopoiesis, CD44 and very late antigen
(VLA)-4. METHODS: In vitro long-term bone marrow cultures were studied in which the effects of blocking antibodies were
assessed by measuring cell numbers and colony-forming units. RESULTS: The blocking of CD44 had a comparable inhibitory
effect on the hematopoiesis of human and pig marrow, even if the latter was maintained on a human stromal layer. Both cellular
proliferation and colony-forming activity were inhibited by anti-CD44 monoclonal antibody. By contrast, a significant difference
was observed in VLA-4 usage by hematopoietic cells of the two species. Blocking VLA-4 markedly inhibited human
hematopoietic cellular proliferation but had no effect on pig hematopoiesis, on either porcine or human stroma.
CONCLUSIONS: The data suggest that the incompatibility of either CD44 or VLA-4 is unlikely to limit the efficiency of
porcine hematopoiesis in a human marrow environment. However, the difference in VLA-4 utilization between these species
raises the possibility that other interactions may be important for effective porcine hematopoiesis and that their failure to function
between species may contribute to the poor function of porcine hematopoietic cells in primate marrow microenvironments.
Macrophage Depletion Promotes Xenogeneic Hematopoietic Chimerism
Background: The successful establishment of xenogeneic tolerance through hematopoietic stem cell engraftment is restricted
by the rapid disappearance of these cells in the recipient following infusion. Therefore, the goal of these studies was to develop
methods to increase survival of pig hematopoietic cell in a xenogeneic recipient. We developed and tested the hypothesis that
the mononuclear phagocyte system was responsible for the rapid clearance of infused pig hematopoietic cells.
Methods: Balb/c or SCID mice were conditioned with a dose of 3Gy whole body irradiation (WBI), heparin, and cobra
venom factor (CVF) on day 0. On various days, mice were injected with medronate-encapsulated liposomes or control blank
liposomes, followed by i.v. infusion of miniature swine bone marrow cells. As a means of measuring mononuclear phagocyte
function, mice were injected i.v. with FITC-labeled latex beads. The kinetics of bead clearance from the circulation were
measured by flow cytometry. To study cell trafficking, swine or autologous bone marrow cells were loaded with a vital
fluorochrome. Bone marrow cells (5x107) were then infused i.v. The kinetics of the disappearance of infused cells from the
circulation and the trafficking through the spleen and into the bone marrow were determined by flow cytometry. Hematopoietic
cells were recovered from the bone marrow at various times and CFU and LTC-IC analyses were performed.
Results: Medronate-encapsulated liposomes are non-toxic in mice at levels that deplete mononuclear phagocytes. Depletion
of mononuclear phagocytes in Balb/c mice as well as in SCID mice increases the accumulation pig hematopoietic cells in the
bone marrow by 10-fold when measured 24hr post bone marrow cell infusion. Following phagocyte depletion, the
accumulation of pig cells in the bone marrow of Balb/c mice is approximately two-fold less than that observed following
autologous bone marrow cell infusion. LTC-IC assays indicate an increased presence of pig progenitors in the bone marrow of
mice which were treated pre- and post- bone marrow infusion with medronate-liposomes. Experiments to investigate the effect
of phagocyte depletion on pig cell chimerism in primates are in progress.
Conclusion: We have found that mononuclear phagocytes play a major role in the elimination of pig hematopoietic cells in
mice. Depletion of mononuclear phagocytes in mice leads to a significant increase in pig hematopoietic chimerism and this
liposome treatment is not toxic to pig hematopoietic progenitors.
This work was supported by BioTransplant, Inc.
Cheng, J., Glaser, R., Cooper, D.K.C., White-Scharf, M.E., and Thall, A.D.
BioTransplant, Inc., Charlestown, MA 02129.
PORCINE PERIPHERAL BLOOD STEM CELL TRANSPLANTATION IN BABOONS IS
COMPLICATED BY THROMBOTIC THROMBOCYTOPENIC PURPURA
In allograft models, the induction of mixed hematopoietc cell chimerism by bone marrow (BM) or peripheral blood stem cells
(PBSC) transplantation (Tx) leads to donor-specific tolerance of subsequently transplanted organs. We are investigating the
induction of mixed chimerism in the discordant pig-to-baboon model. METHODS. Leukopheresis of cytokine-stimulated
(pIL3, pSCF, hGCSF) mobilised PBSC in pigs results in the collection of 30-90x10^10 cells. Pig leukocytes (15-35x10^10)
were transplanted into 3 groups of splenectomized baboons. Group 1 (n=2) received no preparative therapy. Group 2 (n=2)
received whole body (300cGy) and thymic (700cGy) irradiation, ATG, cyclosporine, mycophenolate mofetil, cobra venom
factor, pig-specific cytokines, and extracorporeal immunoadsorption to remove anti-Gal antibodies before PBSC Tx. Group 3
(n=6) received the above regimen combined with prostacyclin, low-dose heparin and methylprednisolone (PHM) +/-
antiCD40L mAb (20mg/kg x2 or x8 doses). RESULTS. Baboons in Groups 1 and 2 developed severe thrombocytopenia
(<10,000cu.mm) requiring multiple platelet transfusions, marked schistocytosis (>12hpf), increase in plasma LDH
(<25,000U/L), loss of high molecular von Willebrand factor (vWF), and mild anemia, transient neurologic changes, renal
insufficiency and clinical purpura. Two baboons died of these complications; autopsy confirmed extensive platelet thrombi in the
microcirculation. (The Group 2 conditioning regimen alone - without PBSC Tx - does not induce these changes.) Group 3
baboons developed moderate thrombocytopenia (not requiring transfusion), mild schistocytosis (<3hpf), mild increase in LDH
(<1000U/L), with no other sequelae, despite loss of vWF. CONCLUSIONS. These data are in keeping with a thrombotic
thrombocytopenic purpura-like state induced in baboons by porcine PBSC Tx, which can be fatal. Prophylactic therapy with
PHM, particularly when combined with anti-CD40L mAb, reduces the sequelae of endothelial activation, markedly reduces
microangiopathic hemolysis, and facilitates the induction of mixed chimerism.
L. Buhler, C. Goepfert, M. Basker, S. Gojo, O. Guckelberger, Q. Chang, K. Nash, A. Watts, S. Treter, G. Oravec,
M. Awwad, A. Shimizu, D. Andrews, M. White-Scharf, D.H. Sachs, S.C. Robson, R. Sackstein, D.K.C. Cooper.
TBRC, Massachusetts General/BI-Deaconess/Harvard Medical School, and BioTransplant, Inc., Boston, USA
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