P962: CHANGE IN SOLUBLE BCMA LEVEL MAY BE A SURROGATE MARKER OF EARLY RESPONSE TO THERAPY IN PATIENTS WITH RELAPSED/REFRACTORY MULTIPLE MYELOMA (RRMM): PRELIMINARY RESULTS FROM A PHASE I STUDY OF CEVOSTAMAB. (23rd June 2022) - Nakamura, R.; Hendricks, R.; Dokhaei, R.; Susilo, M.; Wilson, D.; Trudel, S.; Cohen, A.; Harrison, S. J.; Krishnan, A.; Fonseca, R.; Adamkewicz, J. I.; Li, M.; et al.