Rational design of a poly-L-glutamic acid-based combination conjugate for hormone-responsive breast cancer treatment

Area of Science:

• Oncology
• Polymer Chemistry
• Drug Delivery Systems

Background:

• Breast cancer is the most common cancer globally, with hormone-responsive subtypes prevalent.
• Advanced breast cancer remains a challenge despite endocrine therapy.
• Drug combinations face pharmacokinetic limitations, hindering optimal tumor drug ratios.

Purpose of the Study:

• To design and synthesize novel poly-L-glutamic acid-based combination conjugates for hormone-responsive breast cancer.
• To evaluate the efficacy of a synergistic drug combination (bisdemethoxycurcumin and exemestane) within these conjugates.
• To investigate the impact of drug loading and linker design on conjugate performance.

Main Methods:

• Rational design and synthesis of star-shaped poly-L-glutamic acid conjugates with pH-responsive linkers.
• Characterization of single and combination conjugates, including drug loading and release kinetics.
• In vitro evaluation of cytotoxicity and synergistic effects in monolayer, spheroid, and patient-derived organoid breast cancer models.

Main Results:

• Combination conjugates demonstrated enhanced cytotoxicity and synergism compared to physical drug mixtures.
• Lower drug loading resulted in less compact conjugates with optimal drug release.
• The lead conjugate candidate inhibited proliferation signaling, reduced inflammation, and promoted autophagy in spheroids, outperforming controls in organoid models.

Conclusions:

• Poly-L-glutamic acid-based combination conjugates offer a promising strategy for hormone-responsive breast cancer treatment.
• Rational design, including drug ratio and loading optimization, is crucial for conjugate efficacy.
• Advanced in vitro models are essential for selecting effective polypeptide-based combination drug delivery systems.