Rash most common side effect in Vectibix trials
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The most common side effect observed in ongoing trials of Amgen Inc’s cancer drug Vectibix is skin rash, according to interim analyses of pivotal trials of the drug in colorectal cancer released on Thursday.
Vectibix is already approved in the United States for treating colon cancer patients who have stopped responding to chemotherapy, and Amgen is studying the drug in earlier stages of the disease, as well as in other types of cancer.
One Phase III study of Vectibix, also known as panitumumab, is looking at its effectiveness as a first-line treatment in combination with a chemotherapy regimen known as Folfox, compared with chemo alone.
An interim safety analysis of the first 601 patients in the trial shows that 54 percent of Vectibix patients reported a skin rash, compared with 11 percent of chemo-only patients.
Skin rash and acne have come to be associated with a response to biologic drugs designed to block a protein called epidermal growth factor—a class that includes Vectibix as well as ImClone Systems Inc’s Erbitux.
A mutation in a gene known as KRAS has been linked to a poor response to the drugs.
Amgen said the interim safety results also show Vectibix was associated with diarrhea in 43 percent of patients, nausea in 39 percent and low levels of infection-fighting white blood cells in 38 percent of patients.
The company said updated pooled safety data from around 900 patients in the trial will be presented later this month at a meeting of the American Society of Clinical Oncology (ASCO).
Questions about the safety of Vectibix were raised last year after Amgen said it had discontinued a key clinical trial after finding that colon cancer patients treated only with chemotherapy and Avastin, an antibody drug sold by Genentech Inc , had a better chance of survival than patients who also received Vectibix.
ImClone is slated to present results from a similar trial of Erbitux, as well as results from a key lung cancer trial, at this year’s ASCO meeting.
“I would be really surprised if their results were much different,” than the Vectibix trial findings, said David Chang, head of oncology drug development at Amgen.
He said use of dual biologics proved to be “too much” in this setting, but the combination of Vectibix with chemotherapy appears to be safe.
Amgen said safety results from 1,100 patients in another trial of Vectibix, in combination with a chemo regimen called Folfiri, as a second-line treatment will also be presented at the meeting.
Interim results from that trial show 61 percent of patients in the Vectibix group reported skin rash, compared with 12 percent in the control arm.
Also at the ASCO meeting, results from a Phase I trial of Vectibix in combination with chemo-radiotherapy, for treatment of head and neck cancer, will be presented from an investigator-sponsored study.
An early abstract of the trial results suggests the combination is highly effective in head and neck cancer and a Phase II study is warranted, researchers said.
LOS ANGELES (Reuters)
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