What is the therapeutic mechanism of cycloserine?

Cycloserine (Cycloserine) belongs to a special class of antibiotics and has a different mechanism of action from most common anti-tuberculosis drugs such as isoniazid and rifampicin. It is a molecule with a structure similar to amino acids. After entering the bacterial body, it inhibits the synthesis of bacterial cell walls. The cell wall of Mycobacterium tuberculosis has a unique complex structure and is rich in mycolic acid, which is an important barrier against external environmental and drug attacks. Cycloserine blocks this cell wall synthesis process by inhibiting key enzyme reactions, resulting in the inability of bacteria to grow and reproduce normally.

More specifically, cycloserine mainly inhibits two key enzymes:D-alanine synthase and D-alanine ligase. These enzymes are critical in the cell wall synthesis process; without them, Mycobacterium tuberculosis cannot form a stable cell wall, ultimately leading to the death of the bacterium. This unique mechanism allows cycloserine to maintain good activity in the face of some tuberculosis strains that are resistant to commonly used drugs. Therefore, it is listed by the World Health Organization as one of the important second-line drugs for drug-resistant tuberculosis.

It should be emphasized that cycloserine alone can easily lead to the rapid development of drug resistance in bacteria, so it is almost always used in combination with other anti-tuberculosis drugs in clinical practice. Combining drugs can not only enhance the bactericidal effect, but also reduce the emergence of drug-resistant strains. The mechanism of action of cycloserine determines that it is not a broad-spectrum antibiotic, but more targeted and effective against special infections such as tuberculosis.

In clinical application, doctors usually adjust the dosage according to the patient's drug resistance, comorbidities, and drug tolerance. Since cycloserine can affect the central nervous system, some patients may experience mood swings, headaches or insomnia, so it needs to be used under the guidance of a doctor.

Reference materials:https://en.wikipedia.org/wiki/Cycloserine