Geron did not say why the patients had dropped out
of the trial or if the sponsor, the Mayo Clinic, had stopped the
Geron said the patients in the study would continue to receive the
drug and be monitored according to the study design.
Stifel Nicolaus & Co analyst Brian Klein said the limited
information that Geron released in a regulatory filing on Monday
could call into question the tolerability and durability of the
"It looks like the therapy for a majority of the patients, or at
least a good percentage of the patients, is going to be limited to
less than a year," he told Reuters.
The Mayo Clinic had begun the trial for a group of blood cancers,
known as myeloid malignancies, in November 2012.
"The drug may only be appropriate for patients who have very severe
disease," Klein said.
Geron said that data from the 79 patients would be enough to support
the drug's development.
The company plans to conduct a mid-stage trial testing the drug,
imetelstat, in patients with myelofibrosis — a rare blood disorder — in the first half of the year.
[to top of second column]
Geron said in November that four of the first 18 patients with
myelofibrosis enrolled in the Mayo Clinic's study were free of the
Imetelstat is designed to inhibit telomerase, an enzyme that enables
rapid multiplication of cancer cells.
Geron's shares were down 18 percent at $4.60 in late-morning trading
on the Nasdaq.
(Reporting by Vrinda Manocha in
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