The US FDA has shown a vote of confidence in using minimal residual disease (MRD) as a response endpoint with the accelerated approval of a supplemental indication for Amgen's Blincyto (blinatumomab) to treat adults and children with MRD-positive acute lymphoblastic leukemia (ALL).
It is the first FDA-approved treatment for MRD-positive ALL, which involves the presence of a small amount of detectible cancer cells remaining after treatment, and can be seen as an endorsement of this surrogate measure, which is being explored across other hematologic malignancies. Also see "Minimal Residual Disease 'Coming Soon' As An Approval Endpoint, Celgene Says" - Pink Sheet, 13 December, 2017