This week
we have another targeted candidate - Imetelstat (GRN163L) is a
potent and specific telomerase inhibitor and so far the only drug of its class
in clinical trials.
The idea
behind Imetelstat is following:
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Telomeres and telomerase play essential
roles in the regulation of the lifespan of human cells. While normal human
somatic cells do not or only transiently express telomerase and therefore
shorten their telomeres with each cell division, most human cancer cells
typically express high levels of telomerase and show unlimited cell
proliferation. High telomerase expression allows cells to proliferate and expand
long-term and therefore supports tumor growth. Owing to the high expression and
its role, telomerase has become an attractive diagnostic and therapeutic cancer
target.
And something
went wrong:
Geron Corp. fell $1.62 (56%) to $1.28 on
Monday after discontinuing a Phase II trial of imetelstat following interim
data that showed significantly shorter median progression-free survival in
patients receiving imetelstat plus paclitaxel vs. paclitaxel alone (6.2 vs. 8
months, p=0.028). Geron attributed the data to lower doses of paclitaxel given
to patients in the imetelstat/paclitaxel arm as a result of hematologic
toxicity associated with the combination. The company estimated that imetelstat
patients received about 85% of the amount of paclitaxel that control patients received.
Geron also said an interim analysis of a
Phase II trial in non-small cell lung cancer patients who completed
platinum-based chemotherapy showed that maintenance therapy with imetelstat
improved median PFS vs. observation alone, but the difference was not significant
(2.8 vs. 2.6 months). The company said it is unlikely that it will continue
development of the telomerase inhibitor in breast cancer or NSCLC. Imetelstat
is also in Phase II trials in essential thrombocythemia (ET) and multiple
myeloma (MM), with top-line data expected next quarter.
Well, we
are really sorry. Or
are not? Who will fail next?
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