Antitumor vs. antibacterial antibiotics: Which agent listed below is NOT regarded as a potent antitumor (antineoplastic) antibiotic?

Introduction / Context:
Several antibiotics are used as antineoplastic agents because they interact with DNA or inhibit topoisomerases. Distinguishing antitumor antibiotics from purely antibacterial agents is a frequent exam theme in medical microbiology and pharmacology.

Given Data / Assumptions:

• Anthramycin, Sibromycin, and Neothramycin are listed along with Erythromycin.
• We must select the drug that is not considered a potent antitumor agent.

Concept / Approach:
Antitumor antibiotics (e.g., anthracyclines, actinomycins, and related compounds like anthramycin and sibromycin) bind DNA or interfere with its function, thereby inhibiting cancer cell proliferation. Erythromycin is a macrolide antibacterial that binds the 50S ribosomal subunit to inhibit bacterial protein synthesis; it has no role as an antineoplastic.

Step-by-Step Solution:
Identify which agents are cited as antitumor antibiotics: anthramycin, sibromycin, and neothramycin have antineoplastic activity. Recognize erythromycin as a macrolide antibiotic used for bacterial infections, not for cancer therapy. Therefore, erythromycin is not a potent antitumor agent.

Verification / Alternative check:
Oncology pharmacopeias and classic literature list anthramycin-class agents with antitumor activity, while erythromycin appears only in antibacterial formularies.

Why Other Options Are Wrong:

• Anthramycin: DNA-interacting antitumor antibiotic.
• Sibromycin: reported antitumor antibiotic.
• Neothramycin: antineoplastic antibiotic.

Common Pitfalls:
Assuming all “-mycin” drugs are interchangeable. The “-mycin” suffix spans many classes (macrolides, aminoglycosides, antitumor antibiotics) with very different indications.

Final Answer:
Erythromycin