Homo-BacPROTAC-induced degradation of ClpC1 as a strategy against drug-resistant mycobacteria.

Antimicrobial resistance is a global health threat that requires the development of new treatment concepts. These should not only overcome existing resistance but be designed to slow down the emergence of new resistance mechanisms. Targeted protein degradation, whereby a drug redirects cellular proteolytic machinery towards degrading a specific target, is an emerging concept in drug discovery. We are extending this concept by developing proteolysis targeting chimeras active in bacteria (BacPROTACs) that bind to ClpC1, a component of the mycobacterial protein degradation machinery. The anti-Mycobacterium tuberculosis (Mtb) BacPROTACs are derived from cyclomarins which, when dimerized, generate compounds that recruit and degrade ClpC1. The resulting Homo-BacPROTACs reduce levels of endogenous ClpC1 in Mycobacterium smegmatis and display minimum inhibitory concentrations in the low micro- to nanomolar range in mycobacterial strains, including multiple drug-resistant Mtb isolates. The compounds also kill Mtb residing in macrophages. Thus, Homo-BacPROTACs that degrade ClpC1 represent a different strategy for targeting Mtb and overcoming drug resistance.

Novel Baicalein-Derived Inhibitors of Plasmodium falciparum.

Malaria, a life-threatening mosquito-borne disease caused by Plasmodium parasites, continues to pose a significant global health burden. Despite notable progress in combating the disease in recent years, malaria remains prevalent in many regions, particularly in Southeast Asia and most of sub-Saharan Africa, where it claims hundreds of thousands of lives annually. Flavonoids, such as the baicalein class of compounds, are known to have antimalarial properties. In this study, we rationally designed and synthesized a series of baicalein derivatives and identified a lead compound, FNDR-10132, that displayed potent in vitro antimalarial activity against Plasmodium falciparum (P. falciparum), both chloroquine-sensitive (60 nM) and chloroquine-resistant (177 nM) parasites. FNDR-10132 was evaluated for its antimalarial activity in vivo against the chloroquine-resistant strain Plasmodium yoelii N67 in Swiss mice. The oral administration of 100 mg/kg of FNDR-10132 showed 44% parasite suppression on day 4, with a mean survival time of 13.5 ± 2.3 days vs. 8.4 ± 2.3 days of control. Also, FNDR-10132 displayed equivalent activity against the resistant strains of P. falciparum in the 200-300 nM range. This study offers a novel series of antimalarial compounds that could be developed into potent drugs against chloroquine-resistant malarial parasites through further chemistry and DMPK optimization.

A Live Attenuated COVID-19 Candidate Vaccine for Children: Protection against SARS-CoV-2 Challenge in Hamsters.

Children are at risk of infection from severe acute respiratory syndrome coronavirus-2 virus (SARS-CoV-2) resulting in coronavirus disease (COVID-19) and its more severe forms. New-born infants are expected to receive short-term protection from passively transferred maternal antibodies from their mothers who are immunized with first-generation COVID-19 vaccines. Passively transferred antibodies are expected to wane within first 6 months of infant's life, leaving them vulnerable to COVID-19. Live attenuated vaccines, unlike inactivated or viral-protein-based vaccines, offer broader immune engagement. Given effectiveness of live attenuated vaccines in controlling infectious diseases such as mumps, measles and rubella, we undertook development of a live attenuated COVID-19 vaccine with an aim to vaccinate children beyond 6 months of age. An attenuated vaccine candidate (dCoV), engineered to express sub-optimal codons and deleted polybasic furin cleavage sites in the spike protein of the SARS-CoV-2 WA/1 strain, was developed and tested in hamsters. Hamsters immunized with dCoV via intranasal or intramuscular routes induced high levels of neutralizing antibodies and exhibited complete protection against the SARS-CoV-2 wild-type isolates, i.e., the Wuhan-like (USA-WA1/2020) and Delta variants (B.1.617.2) in a challenge study. In addition, the dCoV formulated with the marketed measles-rubella (MR) vaccine, designated as MR-dCoV, administered to hamsters via intramuscular route, also protected against both SARS-CoV-2 challenges, and dCoV did not interfere with the MR vaccine-mediated immune response. The safety and efficacy of the dCoV and the MR-dCoV against both variants of SARS-CoV-2 opens the possibility of early immunization in children without an additional injection.

Expanding the anti-flaviviral arsenal: Discovery of a baicalein-derived Compound with potent activity against DENV and ZIKV.

With approximately 3.8 billion people at risk of infection in tropical and sub-tropical regions, Dengue ranks among the top ten threats worldwide. Despite the potential for severe disease manifestation and the economic burden it places on endemic countries, there is a lack of approved antiviral agents to effectively treat the infection. Flavonoids, including baicalein, have garnered attention for their antimicrobial properties. In this study, we took a rational and iterative approach to develop a series of baicalein derivatives with improved antiviral activity against Dengue virus (DENV). Compound 11064 emerged as a promising lead candidate, exhibiting antiviral activity against the four DENV serotypes and representative strains of Zika virus (ZIKV) in vitro, with attractive selectivity indices. Mechanistic studies revealed that Compound 11064 did not prevent DENV attachment at the cell surface, nor viral RNA synthesis and viral protein translation. Instead, the drug was found to impair the post-receptor binding entry steps (endocytosis and/or uncoating), as well as the late stage of DENV infection cycle, including virus assembly/maturation and/or exocytosis. The inability to raise DENV resistant mutants, combined with significant antiviral activity against an unrelated RNA virus (Enterovirus-A71) suggested that Compound 11064 targets the host rather than a viral protein, further supporting its broad-spectrum antiviral potential. Overall, Compound 11064 represents a promising antiviral candidate for the treatment of Dengue and Zika.