Although polymers naturally show a slower penetration time, even intact IgM can reach implanted tumours and metastases in patients after i.v. or i.p. administration (Kaveri et al, 2012; Vollmers & Brandlein, 2006), and IgM now represents an attractive vehicle for the delivery of IgM-conjugated drugs into leukemic B cells expressing high levels of FcμR (Vire et al, 2011). Here, CD40LG is linked to neoplasm.