Molecular Partners has presented first patient imaging and dosimetry data for MP0712, its DLL3-targeting radiotherapy candidate, at the Theranostics World Congress 2026, supporting the continued clinical development of the programme in DLL3-expressing cancers.

The data were shared through two poster presentations and one oral presentation at the meeting, which took place in Cape Town between January 29 and February 1. MP0712 is a Radio-DARPin therapeutic co-developed with Orano Med and is being evaluated for the treatment of small cell lung cancer and other neuroendocrine tumours expressing DLL3.

According to the company, the imaging data demonstrate specific tumour uptake and robust accumulation of MP0712 in tumour lesions, alongside limited uptake in healthy tissues. The biodistribution profile and dosimetry extrapolations were described as supportive of the ongoing Phase 1/2a clinical study design using the alpha-emitting isotope 212Pb as the therapeutic payload.

The data were generated from five evaluable patients who received MP0712 labelled with the diagnostic isotope 203Pb. Treatment was administered as part of a named patient access programme under South Africa’s compassionate use framework, also known as Section 21 of the Medicines and Related Substances Act. The work was led by Mike Sathekge at the University of Pretoria and Steve Biko Academic Hospital.

Sathekge said: “I am highly encouraged by the data generated in my group suggesting a favorable distribution profile of MP0712, a DLL3-targeted radiopharmaceutical for patients with SCLC and NEC cancers.”

He added: “During the imaging step with 203Pb, we observed in our patients a promising tumor uptake, paired with a clean profile in healthy organs indicating a therapeutic potential for MP0712. I look forward to seeing this confirmed in the upcoming Phase 1 study.”

Molecular Partners said MP0712 has been engineered with a half-life designed to promote tumour uptake over time through DLL3 internalisation and replenishment mechanisms. Biodistribution was observed across several DLL3-expressing malignancies, including small cell lung cancer, urothelial cancer, and other neuroendocrine tumours, supporting broader development plans beyond a single indication.

The dosimetry data support dose selection and escalation in the ongoing Phase 1/2a study, which is currently open at multiple sites in the U.S. The study is designed to assess safety and establish a recommended Phase 2 dose of MP0712 carrying 212Pb, with an initial imaging and dosimetry step using 203Pb-labelled MP0712.

Patrick Amstutz, chief executive officer of Molecular Partners, said: “The clinical data presented at TWC 2026 validate our assumptions and support the ongoing U.S. Phase 1/2a study, enabling us to initiate dosing of MP0712 within a potentially therapeutic range.”

He added: “The biodistribution and dosimetry data demonstrate exactly what we aim to achieve with Radio-DARPins — strong tumor accumulation with rapid clearance from healthy tissues.”

Amstutz said the company expects to share initial Phase 1 safety and activity data in 2026 as development of the Radio-DARPin platform continues across multiple solid tumour indications.