快猫短视频

LEANER appears to be meaner when it comes to anticancer drugs. A new slimline
drug has caused complete remission in 11 out of 16 patients with one kind of
leukaemia, say doctors in a US report.

The drug, developed by Robert Kreitman鈥檚 team at the National Cancer
Institute near Washington DC, is called BL22. It has been engineered so that one
half is an antibody and the other is a bacterial toxin.

Coupling an antibody with a bacterial toxin isn鈥檛 new in itself. Such
鈥渋mmunotoxins鈥� have been used for over 10 years to treat some tumours, Kreitman
says.

But BL22 belongs to the latest breed of immunotoxins, engineered to be
smaller. 鈥淚t seems that they are better tolerated, so we can treat patients more
often,鈥� Kreitman says. BL22鈥檚 small size lets it target tumours more efficiently
because it can enter the malignant cells quicker, he says.

The drug is a 鈥渧ery important form of biotherapy鈥�, says Lawrence Piro of the
John Wayne Cancer Institute in Los Angeles. It is designed to treat hairy-cell
leukaemia, of which there are about 600 new cases in the US every year.

BL22 works because its antibody portion grabs onto a receptor on the surface
of the leukaemia cells, which then swallow the drug. Once inside, the toxin half
of BL22 hijacks the protein-making machinery of the cell, and effectively kills
it. The toxin is derived from the Pseudomonas bacterium. 鈥淚t鈥檚 a very
powerful enzyme. One [molecule] is enough to kill a cell,鈥� says Kreitman.

Of the 16 patients whose leukaemia resisted conventional chemotherapy, 11 had
a complete remission and 2 had a partial remission after three doses of BL22.
Between one and two years later, 3 of the 11 patients relapsed and were treated
again, and all had a second complete remission. 鈥淚t鈥檚 an excellent remission
rate. That tells you that this molecule is highly active and should be developed
further,鈥� says Piro.

However, agents like BL22 are relatively new, and an editorial in The New
England Journal of Medicine warns of possible adverse effects. Some of the
patients in the trial did suffer from side effects, but they were successfully
dealt with.

While the study focused on the treatment of hairy-cell leukaemia, Kreitman
believes that the antibody-toxin combo will work for other leukaemias. 鈥淎 number
of other diseases seem very appropriate for this kind of treatment,鈥� he says.
Piro points out that chronic lymphocytic leukaemia, the most common form of the
disease, has the same receptor on its cells as hairy-cell leukaemia.