Cancer is one of the leading causes of death worldwide. In the available treatments, chemotherapy is one of the most used, but has several associated problems, namely the high toxicity to normal cells and the resistance acquired by cancer cells to the therapeutic agents. The scientific community has been battling against this disease, developing new strategies and new potential chemotherapeutic agents. However, new drugs often exhibit poor solubility in water, which led researchers to develop functionalized nanosystems to carry and, specifically deliver, the drugs to cancer cells, targeting overexpressed receptors, proteins, and organelles. Thus, this review is focused on the recent developments of functionalized nanosystems used to carry poorly water-soluble drugs, with special emphasis on liposomes and albumin-based nanosystems, two major classes of organic nanocarriers with formulations already approved by the U.S. Food and Drug Administration (FDA) for cancer therapeutics.

The increase in drug resistance and the high toxicity of current drugs have inspired the scientific community to develop new drugs for various diseases. Hydrazides have become an attractive functional group to easily obtain a plethora of novel compounds with a broad range of biological activities. This review, which contains studies in the literature from the previous five years, focuses on the synthesis methods and biological applications of hydrazides and their derivatives. Here, the details of the experimental reaction conditions used for the synthesis of hydrazides and their derivatives (hydrazide–hydrazones and heterocycle derivatives) are presented, as well as the purification methods and the biological activity of the synthesized compounds.

Background/Objectives: Cancer is one of the deadliest diseases worldwide. Despite the existing treatments, the adverse side effects and the increasing drug resistance to the current therapies lead to a reduced quality of life for patients and poor prognosis. The pyrimido[5,4-d]pyrimidine compound (PP) was identified as a promising new anticancer drug due to its potent activity against colorectal and triple-negative breast cancers; however it showed poor aqueous solubility and safety profile. This study aimed the synthesis of compound PP, its encapsulation in liposomal formulations based on phosphatidylcholines (PC), the characterization of liposomal formulations and its biological evaluation. Methods: A new synthesis method for PP was developed. The compound was incorporated into different liposomal formulations. The hydrodynamic size, polydispersity, and zeta potential of loaded and non-loaded formulations were measured by DLS. The cytotoxic effects of compound PP, placebo nanoformulations, and PP-loaded nanoformulations were assessed in colorectal (HCT 116) and triple-negative breast cancer (MDA-MB-231) cell lines, as well as in non-tumor BJ-5ta cells. Results: The PP compound was efficiently synthesized. The PP-loaded liposomal formulations exhibit sizes below 150 nm, low polydispersity, and long-time stability upon storage at 4 °C. The antitumor compound was encapsulated with excellent efficiency, and sustained release profiles were obtained. The PP compound showed high activity against HCT 116 (IC₅₀ = 2.04 ± 0.45 µM) and MDA-MB-231 (IC₅₀ = 5.24 ± 0.24 µM) cell lines. DPPC-containing formulations were effective against cancer cells, but showed toxicity comparable to free PP in BJ-5ta normal cells. Conversely, PP-EggPC-Chol-L formulation displayed strong anticancer activity with residual toxicity to normal cells. Conclusions: The PP-loaded liposomal formulation, composed of 70% PC from egg yolk (EggPC) and 30% cholesterol (Chol), designated as PP-EggPC-Chol-L, was the most promising formulation, showing effective anticancer activity in both cancer cell lines and a significant improvement in the safety profile which is of utmost importance to progress to the next phase of drug development.

A set of 2-aryl-9-H or methyl-6-morpholinopurine derivatives were synthesized and assayed through radioligand binding tests at human A₁, A_2A, A_2B, and A₃ adenosine receptor subtypes. Eleven purines showed potent antagonism at A₁, A₃, dual A₁/A_2A, A₁/A_2B, or A₁/A₃ adenosine receptors. Additionally, three compounds showed high affinity without selectivity for any specific adenosine receptor. The structure-activity relationships were made for this group of new compounds. The 9-methylpurine derivatives were generally less potent but more selective, and the 9H-purine derivatives were more potent but less selective. These compounds can be an important source of new biochemical tools and/or pharmacological drugs.