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ATIR™ data presented at the annual EBMT Presidential Symposium

Amsterdam, The Netherlands, April 8, 2009 – Kiadis Pharma B.V., a clinical stage biopharmaceutical company developing treatments for blood cancers, reported preliminary clinical data on ATIR™ showing its potential in mismatched bone marrow transplantations. Data was presented by the company’s principal investigator Dr. Denis Claude Roy during the prestigious Presidential Symposium at the Annual European Bone Marrow Transplantation meeting (EBMT) in Goteborg, Sweden, on Monday, March 30, 2009. Only the 6 highest ranked presentations, representing the most promising new developments in the transplantation field, were selected for this Symposium.

ATIR™, a donor lymphocyte cell based preparation depleted of allo-reactive T-cells, is under development to prevent acute Graft versus Host Disease (GvHD) and allow for early immune reconstitution following a bone marrow transplantation with a fully mismatched (haplo-identical) donor.

Dr. Roy’s presentation of clinical results from 19 end stage blood cancer patients with high risk leukemia and/or lymphoma using ATIR™ was very well received. These patients, each of whom did not have a matched donor available, were treated in a phase I/II dose escalating study with ATIR™ in a mismatched transplantation setting. No immune suppressants were used, which is in contrast to conventional transplant procedures. Nevertheless, no cases of severe grade III/IV acute GvHD occurred after ATIR™ infusion. Furthermore, the clinical data showed a reduction in the frequency of infectious episodes in the cohorts treated with the higher doses of ATIR™, as compared to the low dose cohorts. To date, patients in the higher dose cohorts show high survival rates (75%) with no transplant related mortality (TRM).

These results show that the selective depletion of allo-reactive T-cells in the ATIR™ cell based product by the proprietary photo-sensitizing agent TH9402 is highly effective and can result in fast and adequate immune reconstitution in combination with the prevention of acute GvHD in bone marrow transplantations using a mismatched donor.

Dr. Denis-Claude Roy, Head of Stem Cell Therapy of the Hospital Maisonneuve- Rosemont, Montreal, Canada says: “These are fascinating results, demonstrating the feasibility of performing mismatched transplantations with an ATIR™ infusion. These results may give hope to patients who currently cannot be treated because of limited donor availability. In the future ATIR™ may allow mismatched transplantations to be performed in virtually all patients who cannot find a donor thereby improving the outcome of the whole procedure.”

Dr. Manja Bouman, CEO of Kiadis Pharma, says: “Kiadis Pharma is pleased with the election of our ATIR™ data to be presented at the Presidential Symposium of the EBMT. It shows the interest in our approach by the medical community. On the basis of these highly encouraging results we are currently preparing for a multinational registration study with ATIR™ in mismatched transplantation procedures.”

About ATIR™

ATIR™ is a T‑cell based medicinal product enabling stem cell transplantations using partially mismatched (haploidentical) family members as donors for patients suffering from blood cancer who do not have a standard of care stem cell donor available. A hematopoietic stem cell transplantation (HSCT) is the only potentially curative option for many patients but a matching donor is available for only half of the patients in need. ATIR™ thus has the potential to address this unmet need and to make an HSCT available for all patients worldwide.

Those T‑cells in a haploidentical graft which would cause Graft-versus-Host-Disease (GvHD) are selectively eliminated using proprietary technology to produce ATIR™. ATIR™ is administered as an adjunctive treatment after a T‑cell depleted haploidentical HSCT facilitating early immune reconstitution without causing life‑threatening (acute) GvHD.

In a Phase I/II study in which high‑risk leukemia patients with very poor prognosis were treated with escalating doses of ATIR™ after a haploidentical HSCT, long‑term safety, efficacy and proof of concept were confirmed in terms of absence of Grade III/IV (life‑threatening) acute GvHD, reduced rates of infection, reduced Transplant Related Mortality and high Overall Survival. Positive follow‑up results from this study demonstrating 67% survival after five years and no Transplant Related Mortality in the nine patients who received an efficacious dose of ATIR™ were recently reported.

An international multi‑center Phase II study including patients with acute myeloid leukemia, acute lymphoblastic leukemia and myelodysplastic syndrome, to corroborate and extend the safety and efficacy results from the Phase I/II study, is now ongoing with topline data expected in the first half of 2014.

ATIR™ has been granted Orphan Drug Designation both in the EU and the USA. Together, both regions represent a combined primary market potential of more than EUR 1 billion per year.

About Kiadis Pharma

Kiadis Pharma B.V. is a private, clinical stage biopharmaceutical company focused on the development of innovative and potentially life‑saving therapies for patients with late stage blood cancers and related disorders, an area of significant unmet medical need.

Kiadis Pharma’s lead product is ATIR™, a cell based product designed to enable stem cell transplantations from partially mismatched (haploidentical) family donors. Kiadis Pharma is collaborating with internationally renowned centers in Europe and North America for the successful development and manufacturing of ATIR™. Kiadis Pharma recently obtained a GMP manufacturing license and GMP certificate for its Quality Control laboratory.

Kiadis Pharma is supported by a strong group of leading international investors including LSP, Alta Partners, DFJ Esprit, Quest for Growth, MedSciences Capital and NOM. Kiadis Pharma is based in Amsterdam, The Netherlands.