After completing the initial 30 mCi cohort with acceptable safety, pharmacokinetics, and biodistribution, the Phase 1 HEAT study of 177Lu-RAD202 in HER2-positive advanced solid tumors will escalate directly to a 75 mCi dose, bypassing the protocol-planned 40 mCi step. Enrollment for the second cohort is slated for Q4 2025, with Radiopharm Theranostics indicating it expects to share readouts from the first two cohorts by year-end.
The core update is a Data Safety and Monitoring Committee greenlight to continue without protocol modifications and accelerate dose escalation. Dosing began in June across Australian centers, reflecting a pattern many radiotheranostic sponsors are following: run first-in-human theranostic programs in a geography with mature nuclear medicine infrastructure and predictable isotope access. RAD202 is a single-domain antibody targeting HER2, leveraging a diagnostic proof-of-concept previously shown in a small breast cancer cohort to anchor the therapeutic program’s biodistribution assumptions.
Strategically, skipping a dose rung is a signal of confidence and a bid to compress time to a recommended Phase 2 dose. In a crowded HER2 landscape defined by ADCs and combinatorial regimens, a beta-emitting Lu-177 approach paired with a small, rapidly clearing binder is a differentiation play around tumor penetration and operational simplicity. The choice of a 75 mCi step remains conservative relative to some Lu-177 regimens but is aggressive relative to the original protocol cadence, suggesting clean early safety and a desire to test a dose that may reveal an efficacy signal sooner. The tradeoffs are familiar to anyone running radiopharmaceutical dose-escalations: marrow suppression and renal exposure are the dose-limiting risks, and sdAbs, while advantageous for tumor access and background clearance, can drive kidney uptake that must be managed with amino acid infusions and tight dosimetry.
Operationally, the move has implications across the ecosystem. Australian sites with on-site radiopharmacies, dosimetry workflows, and SPECT/CT capacity are positioned to enroll quickly, but throughput will still hinge on isotope logistics, infusion chair availability, and radiation safety staffing. CROs and imaging vendors with radiotheranostic credentials will be needed to coordinate central dosimetry, radiation QA, and adverse event attribution that distinguishes hematologic toxicity from prior therapy effects. For sponsors, a faster march to higher doses can reduce cycle time and cost, but it also demands robust real-time data capture, DSMC cadence, and supply chain assurance for both the sdAb construct and Lu-177, ideally, no-carrier-added material to optimize specific activity. Regulators will stay focused on kidney and marrow dose constraints, cycle spacing, and whether the biodistribution profile holds across non-breast HER2-positive histologies such as gastric, colorectal, and biliary cancers.
The near-term signal to watch is whether early objective responses or durable disease control emerge even in dose escalation, alongside clean kidney and hematologic safety at 75 mCi. Clarity on cycle number and inter-cycle spacing will matter, as will evidence that the diagnostic and therapeutic versions of RAD202 are suitably concordant to enable a true theranostic paradigm. If tolerability remains favorable, expect a push to either higher single-cycle dosing or multi-cycle regimens and the design of expansion cohorts that position the asset post-ADC in heavily pretreated settings. A U.S. IND or ex-Australia site activation, isotope sourcing at scale, and manufacturing reproducibility for the conjugate are the executional gates that will define whether the program can move into a 2026 Phase 2 with momentum.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
