A phase-specific drug kills only cells that are in its target phase while the drug is present. The fraction of tumor cells killed therefore depends on two things: how long the drug remains at an effective concentration, and how quickly cells move through the cycle into the sensitive phase. If the drug is present for only a short time, only the cells already in the sensitive phase are killed; the rest survive and can continue to divide. If the drug is present for a longer period, more cells enter the sensitive phase during the exposure and are killed. However, normal tissues with high growth fractions are also exposed for longer, so toxicity increases as well. The simulation lets you vary the infusion duration and the tumor growth fraction to see how the killed fraction changes for tumor and for a representative normal tissue, and to observe the trade-off between efficacy and toxicity.
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This simulation lets you test the scheduling logic directly. Start with a short infusion — say one hour — and a tumor growth fraction of about fifty percent. You will see that only a small fraction of tumor cells is killed, because most cells are not in the sensitive phase during that hour. Now increase the infusion duration. More cells enter the sensitive phase while the drug is present, so the killed fraction rises. But watch the normal-tissue curve: it rises too, because the same logic applies to the high-growth-fraction normal tissues. The goal is to find a duration that kills a useful fraction of tumor cells without pushing normal-tissue kill past a tolerable limit. Try changing the tumor growth fraction as well — a tumor with a higher growth fraction reaches a given kill fraction with a shorter infusion, because more cells enter the sensitive phase per unit time.
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