Methods
We use a response surface model M a ( | Γ , ) b to describe
the difference between the observed percentage inhibition
Introduction
Various oncogenic cell signaling pathways are known to
provide cross-talk and redundancy within tumors.1 Thus,
inhibition of such pathways individually by a single targeted
therapy has been shown to lead to compensation by
other pathways. This, in turn, results in a loss of sensitivity
to the original targeted therapeutic agent at the cellular
level. In the clinic, this type of compensation leads to innate
and/or acquired tumor resistance and relapse.
Because advanced tumors are often resistant to single
agents, there is an increasing trend to combine drugs to
achieve better treatment effect and reduce safety issues.2,3 It
is desirable that the combination drugs are synergistic; that is,
better activity is achieved at lower dose levels when drugs are
combined than individually observed at single drug doses.
Depending on drug doses, drug combinations can yield activity
that is synergistic, independent, or antagonistic.