CD38 and plasma cell myeloma: However, these attempts may be contra-productive if CD38 is in fact a growth and survival factor for myeloma cells as suggested by the prolonged survival of patients obtaining only MR or SD during treatment with Daratumumab in a situation where CD38 expression by the myeloma cells is known to be reduced [7] (Figure 2), and when one take into consideration the modes of action of Daratumumab where either low expression of CD38 is beneficial or continued exposure to Daratumumab is important (Table 2).