TRENTON, N.J. (AP) -- Shares of drugmaker Amgen Inc. climbed Wednesday on news that its innovative melanoma drug, which uses a virus as a Trojan horse to infiltrate and destroy tumors, shrank far more tumors than a standard treatment in a late-stage test.
The partial study results, released late Tuesday, show promise for similar vaccines other companies are developing.
The experimental injected drug made tumors disappear or at least shrink by half for at least six months — what's called the durable response rate — in 16 percent of study participants. That compares with tumor reduction in just 2 percent of patients in a control group that received a standard treatment.
Amgen said its interim analysis indicates the drug, named talimogene laherparepvec but dubbed T-VEC for obvious reasons, showed a trend toward helping patients survive longer than those in the control group. The world's largest biotech company, based in Thousand Oaks, Calif., expects full results on the survival comparison late this year.
Shares of Amgen rose $1.65, or 1.8 percent, to close at $94.05. Earlier in the day, the shares hit an all-time high of $94.89.
"These are the first (late-stage) results of this novel approach to cancer therapy," Dr. Sean E. Harper, head of research and development at Amgen, said in a statement. "A high unmet need exists in melanoma and we believe the innovative mechanism of action of talimogene laherparepvec may offer a promising approach for these patients."
The drug, which works in two complementary ways, combines a gene snippet meant to stimulate the body's immune system with a modified version of the herpes simplex virus — the kind that causes mouth cold sores.
T-VEC is injected directly into tumor tissue, where it divides into copies repeatedly until the membranes, or outer layers, of the cancer cells burst, destroying them. Meanwhile, the gene snippet churns out a protein to stimulate a systemic immune response to kill melanoma cells in the tumor and elsewhere in the body.
How long patients getting T-VEC survive will be crucial to whether regulators decide to approve the experimental drug.
Analysts were split on the likelihood of approval.
RBC Capital Markets analyst Michael Yee wrote to investors that he's "cautious" on the likelihood the full survival results later this year will show T-VEC is better than a couple of existing treatments — and they don't have to be injected into a tumor every two weeks.
However, Mara Goldstein of Cantor Fitzgerald called the findings "a win for immunotherapy."
"We can't help but feel encouraged for other agents in development," she wrote to investors, "particularly in light of the failure" of a study of experimental cancer vaccine Stimuvax, being tested by Merck KGaA of Germany.
She noted Dendreon Corp. already sells a vaccine to treat prostate cancer, Provenge, and a handful of other companies have therapeutic vaccines against breast, pancreatic and brain cancers in late-stage testing.
UBS Securities analyst Matthew Roden noted T-VEC's 16 percent durable response rate in this study, as well as its 58 percent one-year survival rate in an earlier, mid-stage study, both exceed study results for Yervoy, Bristol-Myers Squibb Co.'s melanoma drug. Roden added that T-VEC doesn't have that drug's severe gastrointestinal side effects.
Yervoy, approved in the U.S. two years ago, was the first drug shown to prolong survival in patients with advanced melanoma. Testing showed its one-year survival rate was 46 percent, according to Roden.
Melanoma is the most aggressive skin cancer. It's the cause of 75 percent of all skin cancer deaths, even though the roughly 132,000 new melanoma cases around the world each year amount to less than 5 percent of all skin cancer cases.
Roden wrote to investors that the positive survival trends shown with T-VEC must be strong or Amgen wouldn't have disclosed the trend information publicly.
If the drug is approved, he wrote, it could become a preferred treatment over Yervoy and surpass it in sales. Yervoy had $706 million in sales last year, nearly double what it produced in 2011.
Linda A. Johnson can be followed at https://twitter.com/LindaJ_onPharma