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NEW YORK (TheStreet) -- AstraZeneca's (AZN) - Get Astrazeneca PLC Sponsored ADR Report experimental lung cancer drug AZD9291 was effective in more than 60% of patients who no longer respond to currently approved therapies because of a specific genetic mutation in their tumors.

The new and encouraging AZD9291 data come from a phase I study to be presented at the upcoming American Society of Clinical Oncology (ASCO) annual meeting. ASCO highlighted the AstraZeneca drug in conjunction with the release Wednesday night of thousands of research abstracts ahead of the annual meeting.

AZD9291 is designed to be effective against non-small cell lung cancer containing a genetic mutation known as T790M, which renders tumors resistant to treatment with drugs like Roche's (RHHBY) Tarceva or Boehringer Ingelheim's Gilotrif. Clovis Oncology (CLVS) - Get Clovis Oncology, Inc. Report is developing a similar drug known as CO-1686.

Approximately 15,000 patients in the U.S. have lung cancer containing the T790M mutation.

Both AstraZeneca and Clovis are expected to begin enrolling lung cancer patients this quarter in new, larger clinical trials aimed at getting their respective drugs approved in the U.S. and Europe. Last year, the FDA designated AstraZeneca's AZD9291 as a Breakthrough Therapy.

In the phase I study, 199 patients with advanced non-small cell lung cancer no longer responding to one or more current therapies were treated with different doses of AZD9291. Overall, 51% of patients reported significant tumor shrinkage, including confirmed and unconfirmed responses.

A subgroup of 132 patients was tested to determine if their lung cancer harbored the T790M mutation. Of the 89 patients found to be T790M positive, the AZD9291 response rate was 64%.

By comparison, the response rate to AZD9291 was 23% in the 43 patients with tumors lacking the T790M mutation.

Here are waterfall plots showing response to AZD9291 broken out by T790M status:

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Responses in nearly all patients were still ongoing, with the longest response lasting more than 8 months. Survival data has not yet been reported for AZD9291 in this study.

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AZD9291 appears to be more selective than currently approved lung cancer drugs, resulting in fewer cases of skin acne and rash. The most common adverse events reported in the study were diarrhea (30%), rash (24%) and nausea (17%). Sixteen percent of patients reported more serious, grade 3-4 adverse events.

Five patients were treated for what was described as "interstitial lung disease-like" adverse events during the trial. One case occurred in a patient treated with the 80 mg dose of AZD9291, four others occurred at the 160 mg dose. [Patients in the trial received as much as 240 mg of AZD9291.] All five patients responded to treatment and recovered, but a review of the adverse event is ongoing.

"There is currently no standard treatment for patients with lung cancer who experience disease progression after initial therapy with an EGFR kinase inhibitor. Although it is still a bit early, our study suggests that AZD9291 may offer an effective new therapy option for these patients, without the skin side effects we typically see with existing EGFR inhibitors," said Dr. Pasi Janne of Dana-Farber Cancer Institute and the lead investigator in the study.

Clovis will also be presenting updated data on its lung cancer drug CO-1686 at the ASCO annual meeting, which starts on May 31.

 An abstract describing an early study of CO-1686 was also released Wednesday night. In this study, 88 lung cancer patients no longer responding to current therapies were treated with different doses and formulations of CO-1686. Sixty-three percent of the patients were found to have tumors mutated for T790M.

 Six of 9 (67%) patients with the T790M mutation, treated with a 900 mg BID dose of CO-1686, achieved a partial response. Another two patients (22%) achieved stable disease, with one of these patients going onto have a partial response after switching to the improved formulation of CO-1686.

 Additional efficacy data on 41 patients will be presented at the ASCO annual meeting.

 The most common adverse events reported in CO-1686 treated patients was nausea (25%), fatigue (21%) and impaired glucose tolerance/hyperglycemia (21%). Patients suffering from high blood sugar were being treated with oral glucose-lowering medicines or dose reduction of CO-1686.

AstraZeneca previously reported data on AZD9291 in September 2013. The lung cancer drug is considered an important candidate in AstraZeneca's pipeline. Pfizer is seeking to acquire AstraZeneca, although the $TK billion offer has so far been rebuffed. 

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback;

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