A Phase 1, Multicenter Imaging Study of LNTH-2403 in Participants With Locally Advanced or Metastatic Solid Tumors.

This study is a Phase 1, multicenter, open-label, single-dose study of the safety , imaging, and biodistribution of LNTH-2403 in participants with locally advanced or metastatic colorectal cancer (CRC), head and neck squamous cell carcinoma (HNSCC), non-small cell lung cancer (NSLC) (squamous or non-squamous histology), or triple negative breast cancer (TNBC). The study comprises a Screening Period, an Imaging Period, a Safety Follow-up Period, and a Long term Follow-Up Period (LTFU). The Screening Period will be up to 28 days. Participants will provide written informed consent and eligibility will be confirmed through completion of all screening assessments within 28 days prior to Day 1 administration of LNTH-2403. The Dosing and Imaging Period encompasses Day 1 through Day 5. Participants will receive a single administration of LNTH-2403 on Day 1. Vital signs, ECGs, and blood sampling will be performed just before LNTH-2403 administration and at the timepoints specified in the protocol after LNTH-2403 administration. Participants will undergo a single whole-body single photon emission computed tomography (SPECT)/CT scan anytime between Days 3 - 5 following administration of LNTH-2403. Blood samples will be collected for LNTH-2403 biodistribution analysis on the day of SPECT/CT imaging. The Safety Follow-up Period will include a Safety Follow-up Visit, which may be conducted remotely by telephone or telehealth or at the site at the discretion of the Investigator, on Day 28 (±2 days) to assess concomitant medications and EAs/SAEs and to request a post-treatment biopsy sample, if available. The Long-term Follow-up Period will be conducted to request that participants provide a post-treatment biopsy sample that was obtained ≤ 90 days after LNTH-2403 administration on Day 1and prior to starting a new therapy, if available. The Long-term Follow-up Visit does not need to be completed if a post treatment biopsy sample was obtained at the Safety Follow-up Visit. Participants are eligible to enroll in another investigational protocol after the SPECT/CT scan and other assessments are performed at the timepoint between Days 3 - 5.