AL Amyloidosis is caused by the accumulation of an immunoglobulin light chain protein. Typically, the protein is caused by a malignant or pre-malignant growth of identical, (clonal) lymphocytes or plasma cells that continue to produce these immunoglobulin light chain proteins.
- The function of a normal plasma cell is to produce immunoglobulin proteins, (antibodies). Normally, there are millions of different lymphocytes and plasma cells in the body each producing its own, albeit unique, immunoglobulin protein. Each of us should have millions of different immunoglobulin proteins circulating within the bloodstream to protect us from infection.
- When a lymphocyte, (in patients with lymphoma), or plasma cell, (in patients with multiple myeloma), becomes malignant it replicates uncontrollably and eventually within the body there are billions of these cells which are identical, like clones, at the time of diagnosis. Because these malignant cells are identical, they also produce the same identical immunoglobulin protein. Unfortunately, in the case of people with AL amyloidosis, this overproduced light chain immunoglobulin protein can sometimes have the property of aggregating with itself and eventually interact with other normal proteins such as glycosoaminoglycans, (GAG), and serum amyloid P protein, (SAP), to form amyloid fibrils. The fibrils can accumulate in tissues causing damage to the function of the organ.
- Patients with AL amyloidosis can have the condition while also having a fully malignant, cancerous, process as well, such as Non-Hodgkin Lymphoma, Waldenstrom's Macroglobulinemia, or Multiple Myeloma. Most patients with AL amyloidosis do not have an additional malignant process. Instead, there is a growth of the abnormal cells but these cells are not fully cancerous. In either event, the treatment is generally the same. One must eliminate the proliferating cells to reduce the production of the harmful amyloid protein.
There is no cure for patients with AL amyloidosis but more frequently patients can go into remission with drug therapy. In our experience, the majority of patients surviving the first six months can often start recovering thereafter and can typically live normal or near normal lives for years to come. Remissions when they occur can last a decade or longer in our and other centers' experiences.
Recently, drugs useful to treat multiple myeloma and lymphoma have improved. Since patients with AL amyloidosis often have a similar proliferation of either lymphocytes or plasma cells, these same drugs have been found useful in these patients.
- Melphalan – A chemotherapy drug used in high doses as part of a stem cell transplant.
- Bortezomib – A new agent that blocks the proteasome, an enzyme in all cells, found to be very helpful in patients with multiple myeloma and most recently in patients with AL Amyloidosis.
- Thalidomide – A sleeping pill later found to cause birth defects was found to be extremely effective in treating patients with multiple myeloma. Our group performed a study showing this agent can lead to remissions of over a decade in some patients.
- Lenalidomide – A newer version of thalidomide with fewer side effects and greater efficacy in general.
- Rituximab – Useful for patients with lymphoma, and Waldenstrom's Macroglobulinemia and AL Amyloidosis.
- Cyclophosphamide – Another chemotherapy drug which can target the cells causing AL Amyloidosis.
Peripheral blood stem cell transplantation- Is a procedure that has the promise of leading to a long-term remission in patients with AL Amyloidosis often without the need for further medication. Blood stem cells normally present in the bone marrow are coaxed into the blood stream using a growth factor drug. When these cells are circulating in high numbers, they are collected and then stored alive in liquid nitrogen. A high dosage of chemotherapy is then given, typically melphalan, to eradicate many if not all of the abnormal amyloid producing bone marrow cells. After the drug has had a chance to work and is cleared from the body, the previously stored peripheral blood stem cells are thawed and then reinfused into the body. It typically takes about 11 days for these new stem cells to grow the bone marrow back.
New versions of bortezomib and lenalidomide have been recently released or are in development. We currently have a clinical trial using an oral version of bortezomib called MLN9708 for patients with relapsed AL Amyloidosis. Other novel agents are also showing promise in research studies.