B cells – B cells are a type of white blood cell that forms part of the body's natural defense system. Their role in this system is to make antibodies. B cells are sometimes also called B lymphocytes.2

Chemotherapy – A type of drug used for the treatment of cancer.2

CLL – The abbreviation for chronic lymphocytic leukemia, a type of cancer where the body contains too many "immature" white blood cells (white blood cells are part of the body's natural defense system). These immature white blood cells mostly collect in the blood and bone marrow.2

Complete Remission – Disappearance of all signs and symptoms of cancer, although cancer may still be in the body. Also called complete response.2

Diarrhea – Frequent, watery bowel movements.2

Fatigue – Feeling extreme tiredness, and not able to do everyday things due to lack of energy.2

Follicular Lymphoma – Also called FL. A cancer of the B cell population, which is part of the body's immune system. B cells, also known as B lymphocytes, are found in the lymph nodes and other lymphoid tissues (spleen and bone marrow). Lymphomas start in the lymphoid tissue and can spread to other organs.2-4

Indolent – A type of cancer that grows slowly.2

Neutropenia – A condition in which there is a lower-than-normal number of neutrophils (a type of white blood cell).2

Non-Hodgkin Lymphoma – Also called NHL. Any of a large group of cancers of lymphocytes. NHLs are often marked by lymph nodes that are larger than normal, fever, and weight loss. There are many different types of NHL. These types can be divided into aggressive (fast-growing) and indolent (slow-growing) types, and they can be formed from either B cells or T cells. Indolent types of NHL may be referred to as iNHL.2

Partial Remission – A decrease in the extent of cancer in the body or tumor size in response to treatment. Also called partial response.2

PI3-Kinase, or PI3K – Short for phosphatidylinositol 3-kinase, a protein found inside a B cell. It is one of the molecules that plays a part in the growth of cancerous B cells and normal B cells. The expansion of cancerous B cells leads to the development of follicular lymphoma, chronic lymphocytic leukemia (CLL), and small lymphocytic lymphoma (SLL). PI3K delta is a specific type of PI3K found in B cells.2,5

Placebo – A treatment that does not contain any active ingredients, but looks the same, and is taken in the same way as a real medicine or treatment.2

Primary Endpoint – The main goal or purpose of a study designed to test whether a treatment does what it is intended to.2

Progression – In terms of cancer, progression means either the spreading of cancer to other areas of the body or when the cancer becomes worse.2

Progression-Free Survival (PFS) – In clinical trials, progression-free survival is the duration of time that patients remain alive without their disease becoming any worse.2

Relapse – The return of the signs and symptoms of a patient's disease following a period of improvement.2

Remission – A decrease in or disappearance of signs and symptoms of cancer. In partial remission, some signs and symptoms of cancer have disappeared. In complete remission, all signs and symptoms of cancer have disappeared, although cancer still may be in the body.2

Severe Diarrhea – 6 or more bowel movements more than the patient typically experienced before starting treatment.6

Side Effect – A health problem that occurs when a treatment a patient is taking to help fight their disease also has an unwanted effect on their body.2

SLL – The abbreviation for small lymphocytic lymphoma, a type of cancer where the body contains too many "immature" white blood cells (white blood cells are part of the body's natural defense system). These immature white blood cells mostly collect in the lymph nodes.2

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  1. ZYDELIG® (idelalisib) [Prescribing Information]. Foster City, CA: Gilead Sciences, Inc.; rev October 2020.
  2. NCI Dictionary of Cancer Terms. National Cancer Institute website. Accessed September 15, 2020.
  3. Lymphoma – patient version. National Cancer Institute website. Accessed September 15, 2020.
  4. About non-Hodgkin lymphoma. American Cancer Society website. Accessed September 15, 2020.
  5. Robak P, Robak T. The emerging role of ibrutinib and idelalisib in the treatment of chronic lymphocytic leukemia. J Hematol Transfus. 2013;1(1):1001.
  6. US Department of Health and Human Services. Common terminology criteria for adverse events (CTCAE), Version 5.0. Reference_8.5x11.pdf. Published November 27, 2017. Accessed September 15, 2020.