Screening Thousands of Drugs in Leukemia Patient Samples to Identify Novel Uses for Approved Drugs.

Discovery of novel non cytotoxic drugs for cancer focuses on targets selectively expressed in malignant cells, only testing at the end if they are toxic to patients. We have developed a novel approach to discover these drugs starting at the end; we screen 2.000 approved drugs with proven safety, directly on freshly extracted (ex vivo) blood samples of patients with Chronic Lymphocytic Leukemia (CLL). These screens are enabled by a novel technology platform based on automated flow cytometry we call ExviTech for ex vivo technology.

All screening studies were performed directly on either peripheral blood or bone marrow samples from 44 patients diagnosed with various subtypes of B-cell malignancies, after informed consent. Patient samples were diluted and plated with each of the 2.000 drugs individually, retaining the erythrocyte population and serum proteins to enable clinically relevant concentrations. The experimental assay was setup the same or a day after sample extraction. Each sample was diluted to achieve a leukemic cell concentration of approximately 3,000 cells/μl; then 45μl of the suspension is added to each well of 96-well plates that contain the pharmacological agents (final concentration of 30μM). The compound plates were then sequentially incubated for 24 hours at 37°C with 5% CO2 for screening (sterile conditions). After incubation, the erythrocytes were lysed and the leucocytes incubated with Annexin V-FITC, anti-CD45-APC and anti-CD19-PE added to each well. The plates were then transferred to an automated flow cytometry system where the contents of each well were aspirated and analyzed by a CyAn flow cytometer. Candidates from the primary screens were validated in additional samples with dose-responses, combinations with approved drugs, multiple incubation times, etc…

Analyzing primary screens from 24 CLL patients, three related compounds (Vivia007, Vivia008 and Vivia009) were found to consistently induce apoptosis of nearly all leukemic B-cells from most of the patient samples diagnosed with B-cell chronic lymphocytic leukemia at levels equal to or greater than known CLL active cytotoxic agents. Notably, these candidates are equally effective against samples of p53 mutated patients. These 3 drugs are pharmacologically me-too drugs sharing the same target and mechanism of action, and are non cytotoxic drugs with a known and good safety profile, administered to millions of patients over many years. Validation experiments were done on 20 additional CLL patients and Vivia009 emerged as the most effective agent with an average EC50 of 18.2μM. The mechanism of action is different than the known mechanism of Vivia009 and its class members for their approved indications. Consistent with this observation, only 3 of 15 members of the same pharmacological drug class were efficacious against CLL malignant cells. All 3 Vivia′s candidates were equally efficacious against other B-Cell Malignancies such as B-ALL (pediatric and adult), and Multiple Myeloma. These drugs are not effective in their current oral formulation and require a novel intravenous formulation. Interestingly, kinetics of induction of apoptosis were faster for Vivia009 than for fludarabine, cyclophosphamide and mitoxantrone. Vivia009 requires only 1 hour of incubation with fresh cells to induce maximal apoptosis. This timeline is less than the 3 hours in which Vivia009 was found present at high concentrations in bone marrow of rats using a single intravenous bolus. Thus, Vivia009 seems to fulfill the pharmacokinetic criteria to eliminate all leukemic cells with a single intravenous bolus, which would be a major advantage over current treatments (5-days fludarabine or 3 days FCR). Animal models are ongoing to confirm the non cytotoxic nature of the candidates in the novel IV formulation and the fewer days needed to reach remission, both compared with fludarabine monotherapy.

In summary, our results demonstrate the potential of the ExviTech technology platform as a successful model for the systematic search of new uses for already existing approved drugs directly on patient samples of hematological malignancies. A new drug candidate with excellent safety profile has been identified with similar efficacy ex vivo as the best approved cytotoxic drugs, which is a non-cytotoxic drug with fast kinetics that might enable significantly safer and shorter treatments.

Bennett:Vivia Biotech: Employment. Sapia:Vivia Biotech SL: Employment. Primo:Vivia Biotech SL: Employment. Suarez:Vivia Biotech SL: Employment. Lago:Vivia Biotech SL: Employment. Matoses:Vivia Biotech: Employment. Espinosa:Vivia Biotech: Ana Espinosa, Employment. Tudela:Vivia Biotech SL: Employment. Arroyo:Vivia Biotech SL: Employment. Jackson:Vivia Biotech SL: Employment. Okun:Vivia Biotech SL: Research Funding. Lopez:Vivia Biotech SL: Employment. Gornemann:Vivia Biotech SL: Employment. Diez:Vivia Biotech SL: Employment. González:Vivia Biotech SL: Consultancy. Dominguez-Gil:Vivia Biotech SL: Consultancy. Troconiz:Vivia Biotech SL: Consultancy. Rodriguez de Fonseca:Vivia Biotech SL: Consultancy. Saunders:Vivia Biotech: Consultancy. Montejo:Vivia Biotech SL: Consultancy. Caveda:Vivia Biotech SL: Employment. Orfao:Vivia Biotech SL: Research Funding. Ballesteros:Vivia Biotech SL: Equity Ownership.