Ribociclib / Advanced Breast Cancer / Metastatic Breast Cancer · Phase 1 Trial

Open-Label Study of BBO-10203 in Subjects With Advanced Solid Tumors

ClinicalTrials.gov · September 9, 2026

Preliminary Why this matters to you Expert discussion

Early or partial results. Treat as a signal, not a conclusion.

AI Summary

This is a Phase 1 trial registration for BBO-10203, a PI3Kα:RAS breaker, in patients with advanced solid tumors. The study is recruiting and aims to determine maximum tolerated dose, recommended Phase 2 dose, and safety profile as a single agent and in combination with standard therapies. No results are yet reported in this registry record.

What was studied

Phase 1, Interventional, Non Randomized, Parallel, Open label, Treatment purpose. Solid Tumor, Adult, Metastatic Breast Cancer, Advanced Breast Cancer, HER2 Mutation-Related Tumors, HER2-positive Metastatic Breast Cancer, KRAS Mutant Metasta…; age from 18 Years. Intervention: BBO-10203; BBO-10203 + Trastuzumab; BBO-10203 + Fulvestrant; BBO10203 + Fulvestrant + Ribociclib; BBO10203 + FOLFOX + Bevacizumab. n = 392. 44 sites across 6 countries.

Key findings

Safety

This is a trial registration with no results posted; outcomes and safety data are not yet reported.

Who this may help

This trial is early-stage and will not inform clinical practice until safety, tolerability, and pharmacokinetics are established. Clinicians should await Phase 1 results and subsequent Phase 2 efficacy data before considering BBO-10203 for any indication.

Plain-language summary

This is a Phase 1, first-in-human study registration with no results posted; it describes planned enrollment and safety endpoints only, representing early-stage drug development.

Study design

As stated by the source record.

MethodsPrimary outcome measures: Determination of maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D) of BBO-10203 as a single agent (assessed at Up to approximately 5 years); Percentage of patients with treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), and dose-limiting toxicities (DLTs) (assessed at Up to approximately 5 years); Recommended BBO-10203 dose in combination with trastuzumab, fulvestrant +/- ribociclib, and FOLFOX + bevacizumab (assessed at Up to approximately 5 years)

DesignPhase 1, Interventional, Non Randomized, Parallel, Open label, Treatment purpose

PopulationSolid Tumor, Adult, Metastatic Breast Cancer, Advanced Breast Cancer, HER2 Mutation-Related Tumors, HER2-positive Metastatic Breast Cancer, KRAS Mutant Metasta…; age from 18 Years

Sample size392

InterventionBBO-10203; BBO-10203 + Trastuzumab; BBO-10203 + Fulvestrant; BBO10203 + Fulvestrant + Ribociclib; BBO10203 + FOLFOX + Bevacizumab

Setting44 sites across 6 countries

Reported figures

Quoted from the source exactly as published.

Planned enrollment392

Study phasePhase 1

Primary endpoint 1Determination of maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D) of BBO-10203 as a single agent

Primary endpoint 2Percentage of patients with treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), and dose-limiting toxicities (DLTs)

Primary endpoint 3Recommended BBO-10203 dose in combination with trastuzumab, fulvestrant +/- ribociclib, and FOLFOX + bevacizumab

Follow-up durationUp to approximately 5 years

Clinical bottom line

Caveats

This is a trial registration with no results posted; outcomes and safety data are not yet reported.
Open-label design without control arm; efficacy outcomes are not primary endpoints.
Study is actively recruiting; enrollment and final sample size may differ from estimate of 392.
Follow-up period up to 5 years; current registry record does not indicate which results have been collected or when they will be published.

Evidence assessment

Graded across the dimensions that decide whether you should act, each from what the source actually supports. There is no single score, and where a dimension was not assessed it says so.

Study design

moderate

Open-label Phase 1 design; no blinding, single-arm dose escalation with combination cohorts planned.

Directness

moderate

First-in-human study; primary endpoints are safety and tolerability, not clinical efficacy.

Consistency

insufficient

No comparator arm; no results reported in this registry record.

Risk of bias

limited

Open-label design carries inherent bias risk; early phase carries selection and reporting uncertainty.

Sample adequacy

moderate

Estimated 392 participants across multiple solid tumor cohorts and combination arms; adequate for Phase 1 dose escalation.

What is missing. This record has no key findings. That is a gap in the analysis, not a judgement about the study.

Source abstract

Registry record from ClinicalTrials.gov (NCT06625775). This is a study registration, not published results. Lead sponsor: TheRas, Inc., d/b/a BBOT (BridgeBio Oncology Therapeutics). Recruitment status: RECRUITING. Phase: PHASE1. Study type: INTERVENTIONAL. Enrollment: 392 participants (ESTIMATED). Conditions: Solid Tumor, Adult, Metastatic Breast Cancer, Advanced Breast Cancer, HER2 Mutation-Related Tumors, HER2-positive Metastatic Breast Cancer, KRAS Mutant Metastatic Colorectal Cancer, Metastatic Lung Cancer, Metastatic Colorectal Cancer, Advanced Lung Cancer, HR-positive, HER2-negative Advanced Breast Cancer, HER2-positive Advanced Breast Cancer. Interventions: DRUG: BBO-10203; DRUG: Trastuzumab; DRUG: Fulvestrant; DRUG: Ribociclib; DRUG: FOLFOX; DRUG: Bevacizumab. Primary outcome measures: Determination of maximum tolerated dose (MTD) and/or recommended Phase 2 dose (RP2D) of BBO-10203 as a single agent , Up to approximately 5 years; Percentage of patients with treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), and dose-limiting toxicities (DLTs) , Up to approximately 5 years; Recommended BBO-10203 dose in combination with trastuzumab, fulvestrant +/- ribociclib, and FOLFOX + bevacizumab , Up to approximately 5 years. Brief summary: First in human study to evaluate the safety, tolerability, and pharmacokinetics (PK) of BBO-10203, a PI3Kα:RAS breaker, alone and in combination with other anti-cancer agents in patients with advanced solid tumors.

Follow from this

Taken from the source record, never inferred. Follow any of these and new work involving them reaches your briefing.

RibociclibAdvanced Breast CancerMetastatic Breast CancerTrastuzumabNCT06625775BBO-10203FulvestrantSolid Tumor, AdultTheRas, Inc., d/b/a BBOT (BridgeBio Oncology Therapeutics)