Identification of clinically achievable combination therapies in childhood rhabdomyosarcoma

Area of Science:

• Pediatric Oncology
• Pharmacology
• Cancer Research

Background:

• Systemic therapy has improved outcomes for rhabdomyosarcoma (RMS), but a significant percentage of patients still face progressive or recurrent disease.
• Effective treatments for metastatic or relapsed RMS are limited, highlighting the need for novel therapeutic strategies.
• Targeted therapies are expected to complement existing cytotoxic chemotherapy regimens for RMS.

Purpose of the Study:

• To develop and utilize an in vitro system for evaluating novel drug combinations in RMS.
• To assess the activity of standard-of-care agents and novel targeted therapies, including AZD1775, cabozantinib, and bortezomib.
• To identify synergistic interactions between conventional chemotherapy and targeted agents for potential clinical application in RMS.

Main Methods:

• Tested 8 agents (5 standard, 3 targeted) individually against 4 RMS cell lines at clinically relevant concentrations.
• Evaluated the potential synergy of two-drug combinations.
• Assessed single-agent activity and combination effects using IC50 values and synergy assays.

Main Results:

• Five standard-of-care agents demonstrated single-agent activity.
• The Wee1 inhibitor AZD1775 showed significant single-agent activity with a mean IC50 of 207 ng/ml, below clinically achievable levels.
• Combinations of conventional RMS chemotherapeutics with AZD1775 exhibited largely synergistic activity at higher, clinically achievable concentrations.

Conclusions:

• An in vitro system can effectively prioritize chemotherapeutics and identify novel drug combinations for RMS.
• AZD1775 demonstrates both single-agent efficacy and synergistic potential with conventional chemotherapy in RMS.
• AZD1775 represents a promising targeted agent for further investigation in RMS treatment strategies.