RE: Cohort 518 Jan 2023 21:57
From FDA link and they seem to think the MTD may be difficult to reach in a targetted therapy... 'Most modern oncology drugs, such as kinase inhibitors and monoclonal antibodies, are designed to interact with a molecular pathway unique to an oncologic disease(s) (i.e., targeted therapies).
These targeted therapies demonstrate different dose-response relationships compared to cytotoxic chemotherapy, such that doses below the MTD may have similar efficacy to the MTD
but with fewer toxicities. Additionally, the MTD may never be reached in certain situations.
Compared to, for example, cytotoxic chemotherapies, patients may receive targeted therapies for much longer periods, potentially leading to lower grade but persistent symptomatic toxicities, which can be more challenging to tolerate over time. Nevertheless, the dosage administered in a registration trial(s) (i.e., the trial or substudy designed to evaluate safety and effectiveness and support a marketing application) for these targeted therapies is often the MTD or the highest dosage administered in the dose-escalating trial if the MTD is not defined. This paradigm can
result in a recommended dosage that is poorly tolerated, adversely impacts functioning and quality-of-life, and moreover, affects a patient’s ability to remain on a drug and thereby derive maximal clinical benefit. Additionally, patients who experience adverse reactions from one treatment may have difficulty tolerating future treatments, especially if there are overlapping toxicities.