MyVisionTest News Archive
Jun 15, 2009
Desensitization occurs after long-term use of Avastin
Researchers describe the clinical characteristics of desensitization (tachyphylaxis) to intravitreal Avastin in patients undergoing treatment for exudative age-related macular degeneration (AMD).
A commonly encountered problem in drug therapy is the desensitization of the body to the drug such that it loses its effectiveness over time; a phenomena known as tachyphylaxis. This is a major problem that can be encountered anytime a drug needs to be taken over a prolonged period of time. It is thought that tachyphylaxis occurs most frequently when drugs have a single therapeutic target. Drugs with multiple targets, or combinations of drugs with a variety of targets, seems to be less prone to desensitization.
The investigators retrospectively reviewed the records of 59 consecutive patients treated with Avaastin at the National Eye Institute over a 14-month period and identified cases demonstrating loss of treatment efficacy as revealed by spectral domain optical coherence tomography. We defined tachyphylaxis as a loss of therapeutic response to Avastin 28 ± 7 days after administration in an eye that had previously demonstrated a therapeutic response in the same time interval.
Five patients (six eyes) were identified as developing tachyphylaxis after repeated treatment with Avastin. High-dose Avastin (2.50 mg) did not restore therapeutic response in these patients. Bilateral tachyphylaxis to Avastin was seen after an episode of unilateral postinjection anterior uveitis. After the first treatment of Avastin, the median time taken to develop tachyphylaxis was 100 weeks (range: 31-128 weeks), and the median number of Avastin treatments to the development of tachyphylaxis was 8 treatments (range: 5-10 treatments).
The researchers conclude that tachyphylaxis can occur after long-term intravitreal use of Avastin in patients with AMD. The precise mechanism of tachyphylaxis is unclear, but both local and/or systemic factors may be involved. This is consistent with previous research of tachyphylaxis to intravitreal Avastin.
WHAT IT MEANS TO YOU: There is great concern that patients needing to continue on long-term anti-VEGF therapy will develop drug resistance. This is why, in addition to cost and convenience, it is so important that the number of injections be kept to the absolute minimum necessary to keep the macula dry. Generally speaking, tachyphylaxis occurs less frequently when a drug has multiple biologic targets. For example, if a drug interferes with multiple stages of a biologic process, then resistance will be less common than if it interferes with only one. All currently available anti-VEGF drugs have just a single therapeutic target. Earlier research found that it was possible to decrease desensitization by combining Avastin with an intravitreal steroid.
Read more...
Retina. 2009;29(6):723-731
Tags: Avastin, wet AMD, dosing strategy, tachyphylaxis
Researchers describe the clinical characteristics of desensitization (tachyphylaxis) to intravitreal Avastin in patients undergoing treatment for exudative age-related macular degeneration (AMD).A commonly encountered problem in drug therapy is the desensitization of the body to the drug such that it loses its effectiveness over time; a phenomena known as tachyphylaxis. This is a major problem that can be encountered anytime a drug needs to be taken over a prolonged period of time. It is thought that tachyphylaxis occurs most frequently when drugs have a single therapeutic target. Drugs with multiple targets, or combinations of drugs with a variety of targets, seems to be less prone to desensitization.
Five patients (six eyes) were identified as developing tachyphylaxis after repeated treatment with Avastin. High-dose Avastin (2.50 mg) did not restore therapeutic response in these patients. Bilateral tachyphylaxis to Avastin was seen after an episode of unilateral postinjection anterior uveitis. After the first treatment of Avastin, the median time taken to develop tachyphylaxis was 100 weeks (range: 31-128 weeks), and the median number of Avastin treatments to the development of tachyphylaxis was 8 treatments (range: 5-10 treatments).
The researchers conclude that tachyphylaxis can occur after long-term intravitreal use of Avastin in patients with AMD. The precise mechanism of tachyphylaxis is unclear, but both local and/or systemic factors may be involved. This is consistent with previous research of tachyphylaxis to intravitreal Avastin.
WHAT IT MEANS TO YOU: There is great concern that patients needing to continue on long-term anti-VEGF therapy will develop drug resistance. This is why, in addition to cost and convenience, it is so important that the number of injections be kept to the absolute minimum necessary to keep the macula dry. Generally speaking, tachyphylaxis occurs less frequently when a drug has multiple biologic targets. For example, if a drug interferes with multiple stages of a biologic process, then resistance will be less common than if it interferes with only one. All currently available anti-VEGF drugs have just a single therapeutic target. Earlier research found that it was possible to decrease desensitization by combining Avastin with an intravitreal steroid.
Read more...
Retina. 2009;29(6):723-731
