*Article* **In Vitro and In Vivo Efficacy of a Novel Glucose–Methotrexate Conjugate in Targeted Cancer Treatment**

**Marta Wo´zniak <sup>1</sup> , Gabriela Pastuch-Gawołek 2,3 , Sebastian Makuch <sup>1</sup> , Jerzy Wi´sniewski 4,5 , Tibor Krenács <sup>6</sup> , Peter Hamar <sup>7</sup> , Andrzej Gamian <sup>5</sup> , Wiesław Szeja <sup>2</sup> , Danuta Szkudlarek <sup>1</sup> , Monika Krawczyk 2,3,\* and Siddarth Agrawal 1,8,\***


**Abstract:** Methotrexate (MTX) is a commonly used antimetabolite, which inhibits folate and DNA synthesis to be effective in the treatment of various malignancies. However, MTX therapy is hindered by the lack of target tumor selectivity. We have designed, synthesized and evaluated a novel glucose–methotrexate conjugate (GLU–MTX) both in vitro and in vivo, in which a cleavable linkage allows intracellular MTX release after selective uptake through glucose transporter−1 (GLUT1). GLU–MTX inhibited the growth of colorectal (DLD-1), breast (MCF-7) and lung (A427) adenocarcinomas, squamous cell carcinoma (SCC-25), osteosarcoma (MG63) cell lines, but not in WI-38 healthy fibroblasts. In tumor cells, GLU–MTX uptake increased 17-fold compared to unconjugated MTX. 4,6-O-ethylidene-α-D-glucose (EDG), a GLUT1 inhibitor, significantly interfered with GLU–MTX induced growth inhibition, suggesting a glucose-mediated drug uptake. Glu-MTX also caused significant tumor growth delay in vivo in breast cancer-bearing mice. These results show that our GLUT-MTX conjugate can be selectively uptake by a range of tumor cells to cause their significant growth inhibition in vitro, which was also confirmed in a breast cancer model in vivo. GLUT1 inhibitor EDG interfered with these effects verifying the selective drug uptake. Accordingly, GLU–MTX offers a considerable tumor selectivity and may offer cancer growth inhibition at reduced toxicity.

**Keywords:** glycoconjugates; methotrexate; cancer treatment; glucose metabolism; drug design and discovery; anticancer drugs; targeted therapy; Warburg effect
