- 124I-8H9-directed radioimmuno-PET is safe, distributes well, and shows activity against micro-metastatic desmoplastic small round cell tumor (DSRCT).
Why this matters
- DSRCT is a rare sarcoma with a long-term survival of
- The murine monoclonal IgG1 antibody 8H9 recognizes cell surface antigen 4Ig-B7H3 and binds to 96% of DSRCTs with restricted normal tissue reactivity.
- This is a phase I study of radioiodinated 8H9 to evaluate toxicity, pharmacokinetics, biodistribution, and efficacy.
- Cohorts of 3-6 patients were treated with escalated doses of IP 131I-8H9.
- A prior dose of 2mCi 124I-8H9 IP was used to acquire PET images and biodistribution data.
- Toxicity was monitored clinically and biochemically.
- 41 DSRCT patients received doses of 30-90mCi/m2.
- No dose-limiting toxicities.
- Blood and peritoneal half-times were 32.5h and 14.6h, respectively.
- Median PFS from radioimmunotherapy (RIT) for first remission patients (n=21) undergoing gross total resection followed by RIT and whole-abdominal radiotherapy was 17.9±1.7 months.
- Only 9 patients have relapsed.
- In contrast, patients with gross residual disease pre-RIT or those receiving RIT in ≥2nd remission (n=20) had median PFS of 8.1±3.5 months (P<.05 for pfs and os>
- Recommended phase II dose was 80mCi/m2.
- Phase 1 study, heterogeneous population.
- Could not evaluate disease responses.