Intron A (Interferon alfa-2b, recombinant)
The following drug information is obtained from various newswires, published
medical journal articles, and medical conference presentations.
Intron A is the first adjuvant therapy to surgery that has been
shown to significantly increase relapse-free and overall survival
in subjects with malignant melanoma. The product has previously
received U.S. marketing clearance for treating hairy cell leukemia,
AIDS-related Kaposi's sarcoma, condylomata acuminata, and
chronic hepatitis B and C.
Intron A is an interferon, a group of naturally occurring
proteins that were first discovered as a result of their ability to
prevent viral replication. Additional research has determined that
interferons have anti-tumor effects and are useful in fighting some
types of cancer cells. Intron A is marketed in 72 countries
worldwide for as many as 16 indications.
In 1985, a large, randomized, controlled phase III clinical
trial conducted at 29 centers by the Eastern Cooperative Oncology
Group, in conjunction with the National Cancer Institute, 280
malignant melanoma subjects were randomized to either treatment
with Intron A or observation post surgery. The primary study
objectives were to determine the effectiveness of Intron A in
prolonging relapse-free and overall survival. A marked improvement
in each of these categories was demonstrated.
In the clinical study, the addition of Intron A after surgical
removal of the tumor increased median overall survival of malignant
melanoma subjects by more than 12 months and median relapse-free
survival by 9 months. A 24% improvement in the five-year survival
rate was demonstrated. A 42% improvement in the five-year
relapse-free survival rate was demonstrated for subjects receiving
Intron A therapy.
Side effects included decreased white blood cell counts, fever,
myalgia, anorexia, vomiting/nausea, increased liver enzyme level,
headache, chills, and depression. Side effects were expected and
controllable through dose modifications.
Mechanism of Action
The exact mechanism of action is unknown. Intron A has been
shown to have intracellular, antiviral immunomodulatory, and
antiproliferative effects, in-vitro and in-vivo. These include
effects on intracellular oncogene expression, stimulation of
natural killer and cytotoxic T-cells, microphage activation, and
induction of cytokine production. Antiproliferative effects shown
include slowing of cell division and reversion of tumor cells to a
Malignant melanoma is the deadliest of three main types of skin
cancer; the other two are basal cell carcinoma and squamous cell
carcinoma. Malignant melanoma causes approximately 7,200 deaths in
the United States a year. The incidence of malignant melanoma is
rising 4% each year in the United States., with 34,100 new cases
expected to be diagnosed in 1995, according to the American Cancer