Fusion of thymosin alpha 1 with mutant IgG1 CH3 prolongs half-life and enhances antitumor effects in vivo.

Thymosin alpha 1 (Tα1) is an immunomodulatory polypeptide secreted from the thymus. Tα1 has a wide range of biological functions, such as immunomodulation and endocrine regulation. Tα1 also displays antiviral and antitumor activities. Tα1 has been successfully used in clinical adjuvant therapy for solid tumors to improve the immune response of patients undergoing chemotherapy and radiotherapy. However, the half-life of Tα1 in the body is short, so frequent administration is required to maintain efficacy. In order to improve the pharmacokinetic profile of Tα1, we linked the mutated CH3 (mCH3) fragment of IgG1 (human) to the C-terminus of Tα1 to produce a long-acting fusion protein, Tα1-mCH3. The half-life of Tα1-mCH3 (47 h) was substantially increased compared with that of the parent molecule Tα1 (3 h). In vivo studies indicated that mCH3 fusion retained the original biological activity of Tα1, and Tα1-mCH3 showed slightly better immunomodulatory effect than Ta1. In the 4 T1 and B16F10 tumor xenograft models, Tα1-mCH3 induced a greater abundance of CD4+ and CD8+ T-cells in tumor tissues compared with Ta1. Tα1-mCH3 exhibited better effect in promoting the production of IL-2 and IFN-γ compared with Tα1. Therefore, Tα1-mCH3 more efficiently inhibited the growth of 4 T1 and B16F10 tumors than Tα1. In conclusion, fusion with mCH3 is an attractive strategy to lengthen the half-life and increase the activity of Tα1.

Approaches for the discovery of metallo-ß-lactamase inhibitors: A review.

After more than 80 years of development, ß-lactam drugs have become the most widely used high-efficiency, low-toxic broad-spectrum antibacterial drugs. However, with the widespread use and even abuse of those drugs, the resistance of major pathogens to ß-lactam drugs has increased over years, which has become a thorny problem to the public health. A common mechanism of the resistance to ß-lactams is the producing of ß-lactamases, which can hydrolyze the ß-lactam ring and inactivate these drugs. Metallo-ß-lactamases (MBLs) are one kind of ß-lactamases that require metal ions for their catalytic activities. Although it is a well-known strategy to recover the efficacy of ß-lactams by the combination of ß-lactamase inhibitors, there are still no MBL inhibitors that can be used in clinical practice. Therefore, it is urgent to develop MBL inhibitors. This review outlines the currently discovered MBL inhibitors with an emphasis on various strategies and approaches taken to discover MBL inhibitors, which may lead to diverse classes of inhibitors. Recent progress, particularly new screening methods, and the rational design of potent MBL inhibitors are discussed.

Generation of a novel long-acting thymosin alpha1-Fc fusion protein and its efficacy for the inhibition of breast cancer in vivo.

Thymosin alpha1 (Tα1) is a multifunctional polypeptide involved in immunoregulation, which universally exists in various organs. The clinical application, however, is limited because of its short half-life. The Fc domain of human IgG has functional properties, improving the affinity and serum half-life. In this study, we fused Tα1 to Fc domain of human IgG1 for generation of a novel long-acting fusion protein, termed Tα1-Fc. Tα1-Fc was expressed, purified, and identified. The results showed that Tα1-Fc was more potent than Tα1 in inhibiting the growth of 4T1 and MCF-7 breast cancer cells in vivo. Furthermore, in the 4T1 tumor model the mice treated with Tα1-Fc exhibited higher level of CD4 and CD8 cells compared with that of the mice Tα1 treated. The interferon-γ and interleukin-2 level in the Tα1-Fc-treated mice was higher than that in the Tα1-treated mice. Tα1-Fc could also alleviate immunosuppression induced by hydrocortisone. In summary, Tα1-Fc provides a novel potent strategy to recruit immune cells against tumors and enhance the antitumor activity of Tα1.

Effect of a C-end rule modification on antitumor activity of thymosin α1.

Thymosin α1 (Tα1), a hormone containing 28 amino acids, has been approved in several cancer therapies, but the lack of tumor-targeting hinders its full use in tumor treatment. We designed a new peptide by connecting Tα1 and RGDR, generating a product, Tα1-RGDR, where RGDR is located in the C-end with both tumor-homing and cell internalizing properties (C-end rule peptides, a consensus R/KXXR/K motif). This work aimed to study the antitumor and immunological activities of Tα1-RGDR, and its differences compared with the wild-type Tα1. The antitumor and immunological activities of Tα1-RGDR were measured using the B16F10 tumor and immunologic suppression models. Tα1-RGDR treatment led to significant inhibition of tumor growth at a dose at which Tα1 showed a slight effect in the B16F10 tumor growth model. In the immunologic suppression model, Tα1-RGDR shared almost equivalent immunomodulatory effect with Tα1. These results demonstrated the better therapeutic effects after treatment with Tα1-RGDR compared with Tα1. Moreover, both Tα1-RGDR and Tα1 shared a helical conformation in the presence of trifluoroethanol based on CD spectroscopy. Our dock information of Tα1-RGDR when combined with integrin αvß3 or neuropilin-1 further confirmed previous experimental results. All these findings suggest that Tα1-RGDR might be a useful therapy for tumors by overcoming its wild type limitation of tumor homing.