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Novel tumor-targeted RGD peptide-camptothecin conjugates: synthesis and biological evaluation
Alma Dal Pozzo1, Ming-Hong Ni, Emiliano Esposito
1Istituto di Ricerche Chimiche e Biochimiche G.Ronzoni, via G Colombo 81, 20133 Milano, Italy. dalpozzo@ronzoni.it
Abstract:
Five RGD peptide-camptothecin (CPT) conjugates were designed and synthesized with the purpose to improve the therapeutic index of this antitumoral drug family. New RGD cyclopeptides were selected on the basis of their high affinity to alpha(v) integrin receptors overexpressed by tumor cells and their metabolic stability. The conjugates can be divided in two groups: in the first the peptide was attached to the drug through an amide bond, in the second through a hydrazone bond. The main difference between the two spacers lies in their acid stability. Affinity to the receptors was maintained for all conjugates and their internalization into tumor cells was demonstrated. The first group conjugates showed lower in vitro and in vivo activity than the parent drug, probably due to the excessive stability of the amide bond, even inside the tumor cells. Conversely, the hydrazone conjugates exhibited in vitro tumor cell inhibition similar to the parent drug, indicating high conversion in the culture medium and/or inside the cells, but their poor solubility hampered in vivo experiments. On the basis of these results, information was acquired for additional development of derivatives with different linkers and better solubility for in vivo evaluation.
Insights
New RGD peptide-camptothecin conjugates targeting alpha(v) integrin receptors show promise. Hydrazone-linked conjugates offer potent in vitro anticancer activity, though solubility requires improvement for in vivo efficacy.
Area of Science:
- Medicinal Chemistry
- Oncology
- Drug Delivery
Background:
- Camptothecin (CPT) is an antitumoral drug with limitations in its therapeutic index.
- Alpha(v) integrin receptors are overexpressed on tumor cells, making them a target for cancer therapy.
- RGD peptides exhibit high affinity for alpha(v) integrin receptors and good metabolic stability.
Purpose of the Study:
- To design and synthesize novel RGD peptide-CPT conjugates to enhance the therapeutic index of CPT.
- To evaluate the affinity, cellular uptake, and anticancer activity of these conjugates.
- To investigate the role of different linker chemistries (amide vs. hydrazone) on conjugate performance.
Main Methods:
- Synthesis of five RGD peptide-CPT conjugates with amide or hydrazone linkers.
- Assessment of conjugate affinity to alpha(v) integrin receptors.
- In vitro evaluation of cellular internalization and tumor cell inhibition.
- In vivo activity assessment (where feasible).
Main Results:
- All conjugates maintained receptor affinity and demonstrated tumor cell internalization.
- Amide-linked conjugates showed reduced in vitro and in vivo activity, likely due to linker stability.
- Hydrazone-linked conjugates exhibited potent in vitro anticancer activity, comparable to CPT.
- Poor solubility of hydrazone conjugates limited in vivo evaluation.
Conclusions:
- Linker stability is critical for the efficacy of RGD peptide-drug conjugates.
- Hydrazone linkers show potential for effective drug release and anticancer activity.
- Further development of RGD peptide-CPT conjugates requires optimization of linker chemistry and solubility for improved in vivo performance.
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