Abstract 5012

Background:

Current combination chemotherapy regimens are highly effective for treating acute lymphoblastic leukemia (ALL). Unfortunately, vincristine, a component used in current regimens, generally causes significant neuropathy. The neuropathy is usually reversible, but it can have a negative effect on the treatment of ALL by delaying therapy or requiring reduced drug doses. The focus of this research is on exploring pharmaceutical solutions for minimizing the neurotoxicity of vincristine.

We selected noscapine as a good candidate for use with vincristine. Noscapine, an FDA-approved antitussive, has no known significant side effects and good oral bioavailability, making it relatively easy to administer to children. Noscapine also demonstrates anticancer properties that are currently being studied, with encouraging preliminary results, in a variety of solid and hematological malignancies.

Noscapine has been shown to protect against vincristine-induced demyelination of axons in vitro. In addition, vincristine and noscapine are synergistic in their antiproliferative effects in two leukemic cell lines.

While noscapine has been used as a single anticancer agent, no preclinical or clinical studies examining it in combination with vincristine have been reported.

Objectives:

  1. To evaluate the safety of noscapine and vincristine in combination in vivo

  2. To evaluate the efficacy of noscapine in preventing vincristine-induced neuropathy in vivo

  3. To investigate possible mechanisms for the observed drug interaction

Methods:
Animal studies:

C57BL/6 female mice were used to test the safety and efficacy of noscapine as a protective agent against vincristine-induced neuropathy. Behavioral assays (tail-flick and rotarod) were used to assess neuropathy. Control groups receiving only saline, vincristine, or noscapine were compared to groups of mice receiving a combination of vincristine and noscapine. Independent experiments were performed that varied in drug dose and delivery. Vincristine was given as an intraperitoneal injection twice a week with doses varying from 0.1 to 1.5 mg/kg. Noscapine was administered along with vincristine by injection or ad libitum in the drinking water. Data regarding neuropathy and other observable side effects, including weight loss, were collected. Brain and peripheral organs were collected from euthanized mice, quick-frozen in liquid nitrogen and stored at −80 degrees C.

Mass spectroscopy experiments:

Tissues were homogenized, extracted with methanol and separated using Isolute C2EC SPC columns. Columns were conditioned with methanol, loaded and washed with 5% methanol and eluted with 100% methanol. Separation with liquid chromatography was followed by electrospray ionization and MS/MS analysis using a triple quadrupole-linear ion trap mass spectrometer.

Results:

The combination of vincristine and noscapine resulted in significant toxic effects including ataxia, seizures, and death in our mouse model. Side effects were not observed in mice given only noscapine. Mice given only vincristine had expected neuropathy as measured by the tail-flick and rotarod assays, but no other significant adverse effects. Noscapine had some protective effect against vincristine-induced neuropathy, but the effect was not statistically significant.

Given the adverse neurologic reactions seen, it was hypothesized that noscapine permitted vincristine to cross the blood-brain barrier. Previous studies have shown that noscapine freely crosses the blood-brain barrier, and vincristine is fatal in humans when given intrathecally. Our hypothesis was not supported by analysis of whole brains collected one hour after intraperitoneal injection of vincristine and noscapine (or controls). Mass spectroscopy results showed a decreased uptake of noscapine into brain and peripheral organs in the mice that received noscapine and vincristine in combination. Accumulation of vincristine was unchanged.

Conclusion:

Noscapine has a significant drug-drug interaction with vincristine in mice. The exact mechanism responsible for this interaction remains undetermined, but several hypotheses including effects on transport mechanisms are currently being investigated. Mass spectroscopy data suggests that vincristine alters the pharmacokinetic or pharmacodynamic properties of noscapine. This may limit the use of noscapine as a neuroprotective agent.

Disclosures:

No relevant conflicts of interest to declare.

Topics:
drug interactions, noscapine, vincristine, weight reduction, pharmaceutical solutions, neuropathy, adverse effects, methanol, mass spectrometry, drug dose

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2011 by The American Society of Hematology
2011
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