A targeted therapy is one that is designed to treat the cancer cells and minimize damage to normal, healthy cells. Cancer treatments that “target” cancer cells may offer the advantage of reduced treatment-related side effects and improved outcomes.
Conventional cancer treatments cannot distinguish between cancer cells and healthy cells. Consequently, healthy cells are commonly damaged in the process of treating the cancer, which results in side effects. Chemotherapy damages rapidly dividing cells, a hallmark trait of cancer cells. In the process, healthy cells that are also rapidly dividing (such as blood cells and the cells lining the mouth and GI tract) are also damaged. Treatment-related damage to healthy cells leads to complications of treatment, or side effects. These side effects may be severe, reducing a patient’s quality of life, compromising their ability to receive their full, prescribed treatment, and sometimes, limiting their chance for an optimal outcome from treatment.
There are many different types of targeted therapies that work in a variety of ways. Revlimid® (lenalidomide) is the first to be FDA-approved for the treatment of myelodysplastic syndrome (MDS). Other targeted therapies are being evaluated in clinical trials.
Revlimid: Revlimid is a new type of drug that regulates the immune system, called an immunomodulatory drug. Revlimid is thought to cause anticancer effects in a variety of ways, which include killing abnormal white blood cells, reducing inflammation, and inhibiting growth of new blood vessels.
Clinical trial results demonstrate that Revlimid is highly effective in the treatment of patients with low -risk MDS who are transfusion-dependent and who have a particular genetic abnormality, which is a partial loss of chromosome 5 (5q-). Response to treatment was rapid and long-lasting. Patients experienced an increase in hemoglobin, a component of red blood cells, within approximately one month (4.4 weeks) after the start of treatment. Two-thirds of the patients treated with Revlimid did not require transfusions for nearly one year (47 weeks).
Strategies to Improve Targeted Therapy of MDS
The development of more effective cancer treatments requires that new and innovative therapies be evaluated with cancer patients. Clinical trials are studies that evaluate the effectiveness of new drugs or treatment strategies. Future progress in the treatment of MDS will result from the continued evaluation of new treatments in clinical trials. Participation in a clinical trial may offer patients access to better treatments and advance the existing knowledge about treatment of this cancer. Patients who are interested in participating in a clinical trial should discuss the risks and benefits of clinical trials with their physician. Areas of active investigation aimed at improving the treatment of MDS include the following:
- Antithymocyte globulin ( ATG)
- Gleevec® (imitanib methylate)
- Zarnestra™ (tipifarnib)
Antithymocyte globulin (ATG): Administering a drug that suppresses the immune system—a technique called immunosuppression—appears to provide some benefit in the treatment of MDS. ATG is the best immunosuppressive agent for the treatment of patients with severe aplastic anemia (a type of bone marrow disease) and produces results rivaling those of stem cell transplantation. This drug has also demonstrated activity in the treatment of patients with MDS.
Clinical trial results suggest that over 43% of patients with MDS respond to immunosuppression with ATG. This response lasted nearly two and a half years (29 months) on average. Research has also demonstrated that after 8 months of treatment with ATG, 34% of patients no longer required red blood cell transfusions, 48% no longer required platelet transfusions, and over 50% had improvement in levels of white blood cells.
Gleevec® (imitanib methylate): Gleevec slows or stops the uncontrolled growth of cancer cells caused by a specific genetic abnormality that is the hallmark of chronic myeloid leukemia. Gleevec is the first treatment of its kind to be FDA-approved and is widely used in the treatment of chronic myeloid leukemia. Clinical trials are ongoing to determine whether Gleevec may be effective in the treatment of other cancers, including myelodysplastic syndrome.
Zarnestra™ (tipifarnib): Zarnestra blocks a key enzyme (protein) called farnesyl transferase that is involved in stimulating a cell to grow and replicate in an uncontrolled manner. In this way, Zarnestra slows down or stops the excessive replication of cancer cells.
Zarnestra appears to be an active treatment with limited side effects in the treatment of patients with intermediate or high-risk MDS. On average, patients survived approximately one year after treatment with Zarnestra.
To learn more about treatment techniques that are being evaluated in clinical trials, go to Strategies to Improve Treatment of MDS.
List A, Dewald G, Bennett J, et al. Hematolgoic and cytogenetic (CTG) response to lenalidomide (CC-5013) in patients with transfusion-dependent (TD) myelodysplastic syndrome (MDS) and chromosome 5q31.1 deletion: Results of a multicenter MDS-003 study. Proceedings from the 2005 annual meeting of the American Society of Clinical Oncology (ASCO). Presented May 14, 2005 at a plenary session. Abstract #5.
Lim Z, Killick S, Cavenagh J, et al. European Multi-Centre Study on the Use of Anti-Thymocyte Globulin in the Treatment of Myelodysplastic Syndromes [abstract]. Blood. 2005;106:707a.
Molldrem JJ, Leifer E, Bahceci E, et al. Antithymocyte globulin for treatment of the bone marrow failure associated with myelodysplastic syndromes. Annals of Internal Medicine. 2002;137:156-163.
Kurzrock R, Fenaux P, Raza A, et al. High-Risk Myelodysplastic Syndrome (MDS): First results of international phase 2 study with oral farnesyltransferase inhibitor R115777 (ZARNESTRA™). Blood. 2004;104(suppl 1):Abstract #68.