Pfizer, Glaxo, J&J Grab ASCO Spotlight

BOSTON ( TheStreet) -- New drugs from Pfizer ( PFE) and GlaxoSmithKline ( GSK) that precisely target genetic weaknesses in cancer were given spotlight treatment Wednesday night by the American Society of Clinical Oncology (ASCO) in a preview of its upcoming and closely followed annual meeting.

ASCO officials also highlighted a mid-stage study of Johnson & Johnson's ( JNJ) Zytiga in early-stage (pre-surgical) prostate cancer patients. Later during the ASCO meeting, which starts in two weeks, J&J will present new Zytiga results from a phase III study in more advanced prostate cancer patients.

In all, ASCO released more than 4,500 research abstracts, or clinical summaries, of new cancer drug data Wednesday night in advance of its annual meeting.

This year's ASCO meeting continues a trend toward exploiting new discoveries in the genetic makeup of cancer cells that allow drug makers to develop new therapies capable of directly targeting cancer at its weakest point.

One such drug is Pfizer's Xalkori, which targets abnormalities in the ALK gene that cause cancer cells to develop and grow out of control. Xalkori and a companion diagnostic test for the ALK gene received FDA approval in August 2011 for the 5% of non-small cell lung cancer patients who have mutated ALK genes.

Wednesday, researchers presented new data showing Xalkori stalls tumor growth, and in some cases, completely erases all signs of cancer, in children with select pediatric cancers.

The study enrolled 70 children with advanced neuroblastoma, anaplastic large cell lymphoma (ALCL) and inflammatory myofibroblastic tumors (IMT) that was no longer responding to current treatments. Patients were treated with one of six different doses of Xalkori, administered as a pill twice daily.

Eighty-eight percent (7/8) of patients with ALCL experienced a complete response, meaning they had no detectable disease. Responses have been durable, with patients remaining on Xalkori therapy with no return of their cancer for as long as 18 months. Abnormalities in the ALK gene are present in 80-95% of ALCL cases. Responses were also observed in patients with IMT and neuroblastoma.

"It's remarkable that this targeted oral medication provided such a substantial benefit in these children with highly aggressive cancers, most of whom had already undergone every available therapy," said Dr. Yael Mosse of Children's Hospital of Philadelphia.

Roche's ( RHHBY) Zelboraf was approved in August 2011 for the treatment of melanoma that contains excess levels of a mutation known as V600 in the BRAF gene. This genetic mutation is found in about half of all melanomas.

At ASCO this year, GlaxoSmithKline is presenting data on its own V600 BRAF inhibitor, known as dabrafenib. In a phase I study highlighted by ASCO officials Wednesday, dabrafenib was combined with another experimental Glaxo drug, trametinib, which targets a different, adjacent cancer pathway, with the goal of provoking a stronger tumor response and preventing or delaying treatment resistance.

The phase I study enrolled 125 patients in total with the V600 BRAF mutation. Of those, 77 patients had not been previously treated with Roche's Zelboraf. Among these 77 patients, treatment with various doses of dabrafenib and trametinib yielded a median progression-free survival of 7.4 months. The confirmed tumor response rate was 56%, with four complete responses and 39 partial responses.

The incidence of skin lesions, a common side effect of Zelboraf, occurred less frequently in patients treated with dabrafenib and trametinib.

In a subset of 24 patients treated with 150 mg of dabrafenib and 2 mg of trametinib, the progression-free survival was 10.8 months and overall response rate reached 63%. Results from this dose group were the highest observed in the trial and suggest the combination may be more effective than treatment with Roche's Zelboraf alone, researchers said, although it's difficult to compare across different clinical trials. Glaxo has selected this dose combination for use in upcoming phase III trials.

Lastly, the addition of Johnson & Johnson's Zytiga to hormone therapy before the surgical removal of the prostate eliminated or nearly eliminated cancer in more than one-third of men with localized, high-risk prostate cancer, according to results from a phase II study released Wednesday.

Zytiga is approved for the treatment of patients with late-stage prostate cancer that has spread to other parts of the body and been treated previously with chemotherapy. Wednesday's study suggests that the drug may also be beneficial for men with a much earlier stage of the disease, before surgery is performed to remove their prostate.

In the study, men with localized but high risk prostate cancer were treated with Zytiga in addition to standard hormone therapy. The goal was to reduce or eliminate the tumor cells in patients' prostate before surgical removal.

Following 24 weeks of Zytiga and standard hormone therapy, 34% of patients had eliminated or almost eliminated all traces of cancer from their prostate. The study did not have a control arm, but researchers Wednesday said that historically, standard hormone therapy alone results in about 5% of patients eliminating cancer from their prostate prior to surgery.

The study suggests a role for Zytiga as a so-called "neo-adjuvant" therapy in prostate cancer although larger confirmatory studies will be required. Medivation's ( MDVN) experimental prostate cancer drug MDV3100 is also being studied in the neo-adjuvant setting.

During the ASCO meeting, researchers will present additional data on Zytiga from a phase III study that enrolled patients with advanced prostate cancer that had not yet been treated with chemotherapy.

Abiraterone and MDV3100 work by blocking production of testosterone that fuels the growth of prostate cancer.

--Written by Adam Feuerstein in Boston.

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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; click here to send him an email.