Treatment with HPMA copolymer-based doxorubicin conjugate containing human immunoglobulin induces long-lasting systemic anti-tumour immunity in mice

Abstract

Linkage of doxorubicin (Dox) to a water-soluble synthetic N-(2-hydroxypropyl)methacrylamide copolymer (PHPMA) eliminates most of the systemic toxicity of the free drug. In EL-4 lymphoma-bearing C57BL/6 mice, a complete regression of pre-established tumours has been achieved upon treatment with Dox-PHPMA-HuIg conjugate. The treatment was effective using a range of regimens and dosages, ranging from 62.5 to 100% cured mice treated with a single dose of 10-20 mg of Dox eq./kg, respectively. Fractionated dosages producing lower levels of the conjugate for a prolonged time period had substantial curative capacity as well. The cured mice developed anti-tumour protection as they rejected subsequently re-transplanted original tumour. The proportion of tumour-protected mice inversely reflected the effectiveness of the primary treatment. The treatment protocol leading to 50% of cured mice produced only protected mice, while no mice treated with early treatment regimen (i.e. starting on day 1 after tumour transplantation) rejected the re-transplanted tumour. Exposure of the host to the cancer cells was a prerequisite for developing protection. The anti-tumour memory was long lasting and specific against the original tumour, as the cured mice did not reject another syngeneic tumour, melanoma B16-F10. The immunity was transferable to naïve recipients in in vivo neutralization assay by spleen cells or CD8(+) lymphocytes derived from cured animals. We propose an effective treatment strategy which eradicates tumours without harming the protective immune anti-cancer responses.

Antitumor activity of IL‐2/anti‐IL‐2 mAb immunocomplexes exerts synergism with that of N‐(2‐hydroxypropyl)methacrylamide copolymer‐bound doxorubicin conjugate due to its low immunosuppressive activity

“…For schematic structure of polymeric conjugate, see Supporting Information Figure 1. It has been shown previously that such a conjugate has considerable antitumor activity in various tumor models in vivo, 3,4 and it has been also successfully used in five patients with metastatic mammary carcinoma. 5,6 It was also demonstrated that this polymeric conjugate has a much longer half-life in circulation than free doxorubicin.…”

Overcoming Immunoescape Mechanisms of BCL1 Leukemia and Induction of CD8+ T-Cell–Mediated BCL1-Specific Resistance in Mice Cured by Targeted Polymer-Bound Doxorubicin

“…It is of special note that our targeted conjugate has negligible immunosuppressive activity (1,4), and thus, nonimpaired immune system is ready to elicit BCL1-specific response. As we showed in this study, BCL1 cells are theoretically capable of antigen presentation to both CD4 + and CD8 + T cells but in tolerogenic/proapoptotic fashion.…”

“…It was reported previously that conjugates based on poly(HPMA) containing doxorubicin are capable to completely cure tumorbearing mice and that some of these mice show tumor-specific resistance (1,4). The goal of our study was to investigate this resistance; specifically, we aimed to determine which subset of immunocompetent cells is necessary for the establishment and which for the maintenance of the resistance.…”

“…B1 mAb specifically binds with high affinity to an idiotype of surface IgM on BCL1 leukemia (3). Thus, we used a conjugate containing potent cytostatic drug specifically targeted to BCL1 cells (2), which enabled us to effectively treat mice bearing the leukemia while causing only minimal damage to the immune system (1,4).…”

“…In this study, we used a conjugate of a synthetic, water-soluble, and biocompatible copolymer based on N-(2-hydroxypropyl)methacrylamide (HPMA) with doxorubicin bound via a Gly-Phe(D,L)-Leu-Gly spacer (1,2) and containing either human polyclonal (i.e., nonspecific) antibody or B1 monoclonal antibody (mAb). B1 mAb specifically binds with high affinity to an idiotype of surface IgM on BCL1 leukemia (3).…”