Candidate drugs and other compounds can be toxic to the sensitive cells of the bone marrow, primarily the blood-forming progenitor cells. The typical physiological consequence of bone marrow toxicity (hemotoxicity or hematotoxicity) is myelosuppression.
Myelosuppression (also known as bone marrow suppression) is a condition where the bone marrow has been adversely affected, resulting in lowered blood cell numbers. Chemotherapies and other therapeutic agents, toxic substances and immune modulating agents often cause one or more types of myelosuppression by affecting the viability, proliferation or differentiation potential of the progenitors of the various blood cell lineages. Any or all lineages of blood cells may be affected. Neutropenia results when an agent is toxic to the myeloid (neutrophil; a type of white blood cell) progenitors, while severe anemia is caused by toxicity of the erythroid (red blood cell) progenitors and thrombocytopenia is the result of toxicity to the progenitors of the megakaryocytic (platelet) lineage. Whether these effects are direct or indirect, our scientists are experts at evaluating the adverse effects using powerful and functional in vitro CFC (colony forming cell) assays. These assays utilize normal bone marrow progenitor cells from human, mice, rats and other species, making them both relevant and predictive. Click here to see an example of how the results from our in vitro assays correlate with clinical myelosuppression. Additionally, we now offer assay services to evaluate lymphopenia. Toxicity of lymphoid lineage (T cell, B cell, NK cell) cells in measured by flow cytometry and CFC assays (mouse Pre-B only) utilizing cytotoxicity assays.
Not all drugs may act on the early progenitors but rather on the cells as they mature from multipotential stem cells to mature granulocytes, red blood cells and platelets. Our cellPrism® platform can assess the generation of these mature cell populations from primitive CD34+ cells and address at what stage of maturation the candidate drug is acting.
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Types of Myelosuppression and Related Assays:
Neutropenia & Myeloid Toxicity (CFU-GM, CFU-G)
Neutropenia is a hematological condition that is characterized by abnormally low numbers of neutrophils in the blood.
Clinical neutropenia is often caused by toxicity of a substance (e.g. drug or toxic agent) to the myeloid progenitors resident in the bone marrow. The number and functionality of myeloid progenitors can be accurately evaluated in the CFU-GM assay, an in vitro Colony Forming Cell (CFC) assay. This makes the CFU-GM assay an excellent model for assessing the myelotoxic potential of new clinical compounds and predicting the level of clinical neutropenia they may cause. The sensitivity of CFU-GM assays often produces results with such a high correlation to observed clinical neutropenia that this assay can even be used to rank each compound within a tested series for the level of clinical neutropenia they are likely to cause if given to patients.
Thrombocytopenia & Megakaryocyte Toxicity (CFU-Mk)
Thrombocytopenia is characterized by any disorder where there is an abnormally low number of platelets in peripheral blood.
Clinical thrombocytopenia is often caused by substances (e.g. drug or toxic agent) that are toxic to the resident megakaryocyte progenitors in the bone marrow. The number and functionality of megakaryocyte progenitors can be accurately evaluated in the CFU-Mk assay, an in vitro Colony Forming Cell (CFC) assay. This makes the CFU-Mk assay an excellent in vitro model for evaluating new drug candidates for their potential to cause thrombocytopenia in the clinic.
Anemia is a condition in which there is an abnormally low number of red blood cells in the blood.
Clinical anemia is often caused by substances (e.g. drugs or toxic agents) that are toxic to the erythroid progenitors resident in the bone marrow.The number and functionality of erythroid progenitors can be accurately evaluated in the BFU-E assay. This makes the BFU-E assay an excellent in vitro model for evaluating new drug candidates for their erythrotoxic potential and for predicting the likelihood that the compounds would cause clinical anemia if given to patients.
Lymphopenia & Lymphoid Toxicity
Lymphopenia is a hematological condition that is characterized by abnormally low numbers of lymphocytes in the blood.
Lymphopenia may be caused by a reduction of T cells, B cells, or NK cells or a combination of all three. Within the T cell population there can be selective effects on T cell subsets, some of which may be useful for understanding the mechanism of action of compounds. Certain therapies, often (but not always) targeting NHL (Non-Hodgkin Lymphoma) related diseases, cause off target cell death of lymphocytes (T cells, B cells and NK cells). The toxicity can be species-dependent. For example, some drugs can cause severe lymphopenia in small animal models, but have little toxicity on human cells.
Cytotoxic assays are used for assessing lymphopenia in primary cells in response to test compounds. Flow cytometry is the optimal method for this assay. The broad spectrum of available antibodies with multiple fluorochromes allows for the simultaneous analysis of the multiple lymphoid subpopulations within the same sample.