This is a phase 1/2a, open-label, dose escalation study conducted in adult participants
with p53 wild-type refractory solid tumors. The study will assess the safety, efficacy,
and pharmacokinetics of SA53-OS a novel MDM2 inhibitor capable of selective activation of
p53. This enables the p53 tumor suppressor protein to selectively facilitate tumor cell
death and growth inhibition.
The study drug, SA53-OS, will be administered for 3 consecutive days every 3 weeks as an
oral solution. Phase 1 will consist of a dose escalation study to establish a candidate
recommended phase 2 dose (RP2D). Phase 2a will enroll 2 expansion cohorts to establish
any preliminary efficacy of SA53-OS in participants with dedifferentiated liposarcoma (DD
LPS) with MDM2 amplifications and other p53 wild-type solid tumors as a single agent.
Phase 1 dose escalation:
Escalating doses of SA53-OS will be provided to participants with p53 wild-type
refractory solid tumors to determine the RP2D. The MTD is the highest dose of a drug or
treatment that does not cause unacceptable side effects in the first cycle. The RP2D
considers all available safety, pharmacokinetics, and efficacy data including, the
frequency, severity, and manageability of toxicities occurring after Cycle 1.
Phase 1 of the study will start with dose escalation by 2-fold (i.e., 2x preceding dose
level) in cohorts of a single participant until Grade 2 or greater toxicity is observed.
When a single Grade 2 or higher toxicity is observed, 3+3 multi-participant cohorts will
be treated at the dose in which the Grade 2 or higher toxicity was observed by enrolling
another 2 participants at this dose. The 3+3 multi-participant cohorts will follow the
standard 3+3 paradigm based on occurrence of any DLT with 50% dose escalation until the
MTD is identified.
Phase 2a dose expansion:
The purpose of Phase 2a of the study is to describe any preliminary evidence of efficacy
from SA53-OS monotherapy in participants with DD LPS or other p53 wild-type or MDM2
amplified solid tumors. Phase 2a will also be used to confirm the safety and tolerability
of the candidate RP2D of SA53-OS determined in Phase 1 of the study, to further describe
the toxicity and pharmacokinetics profiles of SA53-OS, and to assess potential biomarkers
of sensitivity resistance, and toxicity.
Participants will continue to receive study treatment until either: 1) disease
progression; 2) occurrence of unacceptable treatment-related toxicity as per participant
or Investigator discretion; 3) the maximum of 2 years of treatment has been reached; or
4) other reason(s) for study treatment discontinuation. In the case of complete response,
treatment should be continued for at least 6 months if no other stopping criteria are
met, and further treatment can be recommended at the investigator's discretion.