Author(s): Correia, Carla ; Leite, Ana Claúdia ; Fraga, Alexandra G. ; Proença, M. Fernanda R. P. ; Pedrosa, Jorge ; Carvalho, M. Alice
Date: 2024
Persistent ID: https://hdl.handle.net/1822/97747
Origin: RepositóriUM - Universidade do Minho
Subject(s): 6-Carbamoylpurines; Neglected tropical disease; New antituberculosis agents; Purine derivatives; Tuberculosis
A series of novel 9-alkyl/aryl-2-aryl-6-carbamoylpurines were synthesized, and their activity against $\text{Mycobacterium tuberculosis}$ strain $\text{H}37\text{Rv}$ was assessed. The $\text{SAR}$ analysis on the first set of derivatives, with an alkyl or aryl unit at $\text{N}$-$9$ and a phenolic unit at $\text{C}$-$2$, showed that the activity depends on the purine ring substituents at $\text{N}$-$9$ and $\text{C}$-$2$. A phenyl group at $\text{N}$-$9$ combined with a $3$-hydroxyphenyl or $4$-hydroxyphenyl at $\text{C}$-$2$ improve the activity. The most active compound of this set has a phenyl group at $\text{N}$-$9$ and a $4$-hydroxyphenyl group at $\text{C}$-$2$, displaying an $\text{IC}_{90} = 1.2\ \mu\text{g/mL}$ and a selectivity index higher than $25.5$. This compound served as a Hit to design the second set of derivatives. A phenyl group at $\text{N}$-$9$ was maintained, and the group at $\text{C}$-$2$ was diversified. The $\text{SAR}$ analysis showed that the aryl unit at $\text{C}$-$2$ must have an oxygen or nitrogen atom bonded in the $\text{para}$ position. A proton, a small alkyl or a substituted aryl group may also be bonded to the oxygen. The compound with the $4$-methoxyphenyl group at $\text{C}$-$2$, $\mathbf{1Bd}$, exhibits the highest activity with an $\text{IC}_{90} < 0.19\ \mu\text{g/mL}$. This compound is highly potent against $\text{M. tuberculosis}$ strain $\text{H}37\text{Rv}$ and non-toxic for $\text{VERO}$ mammalian cells with an $\text{SI} > 153.8$. Compound $\mathbf{1Bd}$ was also non-cytotoxic against primary macrophage cultures at $\text{IC}_{90}$, $2 \times \text{IC}_{90}$, and $10 \times \text{IC}_{90}$ and significantly reduced the bacterial load in $\text{M. tuberculosis}$-infected macrophages at the same concentrations. Compound $\mathbf{1Bd}$ showed a favorable pharmacokinetic profile when administered orally, with major lung and liver accumulation. $\text{In vivo}$ antimycobacterial efficacy of $\mathbf{1Bd}$ was tested at $25\ \text{mg/kg}$. At the tested regimen, a decrease in bacterial burden was observed in the liver. Optimization of the treatment regimen should be performed to fully potentiate the $\text{in vivo}$ efficacy of our lead molecule, particularly in the lung, the main target organ of $\text{M. tuberculosis}$.
