At or in an intermediate stage, between beginning and completion(noun)
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Use "midstage" in a sentence
"The Cambridge, Mass., drug developer also reported that the outcome of a midstage trial of the drug in a more common form of the disease failed to show significant effectiveness."
"Mr. Porges recently said the midstage study, called Discover, was unlikely to show a similar response to the late-stage Strive study because VX-770 was designed specifically to address a mutation known as G551d."
"And on Monday, Exelixis Inc. reported promising results from a midstage, or Phase II, study of its drug cabozantinib, in advanced prostate cancer."