* Six patients die from cabo-related side effects
* Rival Bayer/Algeta drug shown to boost survival
* CEO says safety results consistent with similar drugs
* Prostate cancer bone metastases shrank in 3/4 patients
* Shares fall 20 percent
(Updates with details of Bayer/Algeta drug results, analyst
comment, closing share price)
By Deena Beasley
CHICAGO, June 6 Shares of Exelixis Inc (EXEL.O)
fell 20 percent on Monday after the company reported data over
the weekend showing that its experimental cancer drug caused
the deaths of six patients in a clinical trial.
Analysts said Exelixis shares were also affected by new
trial results showing that a rival drug being developed by
Bayer (BAYGn.DE) and Algeta ALGETA.OL helped prostate cancer
patients live longer.
The Phase 2 data presented here at a meeting of the American
Society of Clinical Oncology showed that treatment with the
Exelixis drug, cabozantinib, led to significant tumor shrinkage
in several different types of solid tumors, including 24
percent of patients with metastatic ovarian cancer.
Exelixis Chief Executive Michael Morrissey said the safety
statistics are consistent with targeted cancer therapies like
cabozantinib that block a pathway used by tumor cells to secure
Cowen & Co analyst Eric Schmidt said the rate of
treatment-related deaths, 1 percent, was "no different from
what we have seen for every other Phase 1 and 2 trial here at
Interim results from the midstage trial also showed that
cabozantinib shrank bone malignancies in 76 percent of prostate
Of 108 prostate cancer patients so far evaluated by bone
scan, 21 had complete resolution, and 61 had partial shrinkage
of metastatic bone lesions, which can lead to bone fractures,
severe pain and eventual death.
The disease remained stable in 23 other patients, or 21
percent, and worsened in three.
For the overall trial, which involved several different
types of solid tumors, six patients died from
cabozantinib-related side effects: one breast cancer patient
from respiratory compromise, one lung cancer patient from
hemorrhage, one ovarian cancer patient from bowel perforation
and another from intestinal perforation, one pancreatic patient
from gastrointestinal hemorrhage and one unexplained prostate
cancer patient death.
"While drug safety is of less concern in cancer indications
than in others, the apparent morbidities associated with cabo
use will confound interpretation of clinical benefit in a trial
designed to show anything less than overall survival,"
Canaccord analyst George Farmer said in a research note.
Morrissey said the company plans to start a Phase 3
prostate cancer trial in the second half of this year with a
combined goal of reducing pain and bone malignancies.
Piper Jaffray analyst Edward Tenthoff also said the
reported deaths were affecting shares of Exelixis on Monday.
"The company is exploring lower doses, but the concern is
that cabo will not retain the impressive efficacy seen to
date," he said in a note to investors.
Morrissey said Exelixis plans to move forward with the
current daily 100 mg dose of the drug.
Exelixis expects to have initial results around midyear
from a trial of the drug as a treatment for thyroid cancer.
Cabozantinib, also known as XL184, is an oral drug designed
to limit blood supply to tumors and block two segments of a
pathway used by cancer cells to grow and spread.
The Bayer/Algeta drug, Alpharadin, is designed to treat
patients with advanced disease whose cancer has spread to their
bones. It works by mimicking many of the behaviors of calcium
in the bone.
Shares of Exelixis fell $2.20 to close at $8.69 on the
Nasdaq, off an earlier low at $8.03.
(For more on the ASCO meeting in Chicago, see:
(Editing by Matthew Lewis, Maureen Bavdek, Dave Zimmerman and