Antibody drug conjugates (ADCs), consisting of a cancer-specific antibody and cytotoxic payload, are shown to be a potent class of anticancer therapeutics, with enhanced therapeutic efficacy and reduced "off-target" side effects. However, the therapeutic window of ADCs is narrowed by problems such as difficulty in site-specific conjugation of payload, changes in antibody stability due to payload conjugation, and difficulty in tissue penetration. In this respect, aptamers have advantages in drug-delivery, as they can be easily and stably conjugated with cytotoxic drugs. We previously reported that oligobody, an aptamer-antibody complex, is a novel delivery method for aptamer-based therapeutics. In the current study, we describe DOligobody, a drug-conjugated oligobody comprising an aptamer-drug conjugate and an antibody. A cotinine-conjugated anti-HER2 aptamer (cot-HER2apt) was specifically bound to HER2-positive NCI-N87 cells, and underwent receptor-mediated endocytosis. Further, HER2-DOligobody, a cot-HER2apt-conjugated monomethyl auristatin E (cot-HER2apt-MMAE) oligobody, inhibited the growth of HER2-positive NCI-N87 cells. Finally, systemic administration of HER2-DOligobody significantly reduced tumor growth in a xenograft mouse model. Taken together, these results suggest that our DOligobody strategy may be a powerful platform for rapid, low-cost and effective cancer therapy.

Several folate-drug conjugates are currently undergoing clinical trials for application in oncology. However, the efficacy of folate-targeted therapy strongly depends on the folate receptor (FR) abundance at the surface of cancer cells. Recently, it has been postulated that up-regulation of FRa by means of chemo-sensitizing agents could enhance the anticancer activity of FR-drug conjugates. In this study, we demonstrate in vitro that a combination of dexamethasone (Dexa) and valproic acid (VPA) increases FR alpha expression selectively at the surface of FR-overexpressing cancer cells. The same stimulation was observed in vivo in KB-tumor xenografts when mice are treated with this combined treatment. This effect is reversible since treatment interruption induces the return of FR expression at basal level. When incubated with Dexa and VPA, the beta-galactosidaseresponsive folate-monomethyl auristatin E (MMAE) conjugate, called MGAF, exhibits higher cytotoxic activity on several FR-positive human cancer cell lines, compared to its administration as a single agent. This improved toxicity results from the enhanced concentration of MMAE released within cancer cells after internalization and subsequent enzymatic activation of MGAF. Higher deposition of MMAE is also observed in vivo after up-regulation of FR expression level in tumor xenografts, induced by the prior administration of the Dexa/VPA combination. In this model, MGAF/Dexa/VPA combined therapy results in an 81% inhibition of tumor growth compared to the control group, while MGAF used in monotherapy is inefficient. Since Dexa and VPA are currently used in humans, this finding could be of great interest for further development of folate-drug conjugates, in particular for those that are presently under clinical investigation.