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NCT Number: NCT07812805

SKL35501 With SKL35502 Imaging in Adults With NTSR1 Positive Advanced Solid Tumors

This Phase 1, open-label study will evaluate two investigational radiopharmaceuticals in adults with selected advanced or metastatic solid tumors. SKL35502 is an imaging agent used with SPECT scans to identify tumors with neurotensin receptor 1 (NTSR1), a protein found on some cancer cells, and to assess where the agent travels in the body and the radiation dose delivered to tissues. Participants with sufficient SKL35502 tumor uptake may receive SKL35501, a treatment designed to deliver targeted alpha radiation to NTSR1-expressing tumor cells.

Part A will evaluate the safety and imaging performance of SKL35502 and the safety, tolerability, pharmacokinetics, biodistribution, dosimetry, and biologically active dose range of SKL35501, as well as preliminary antitumor activity. Part B will further evaluate selected SKL35501 dose levels, including randomized low- and high-dose groups in participants with colorectal cancer, and will expand evaluation in selected tumor types. The study will also examine relationships among SKL35502 imaging, NTSR1 expression, SKL35501 tumor uptake, and treatment outcomes.

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Key information

Conditions

Selected Advanced Solid Tumors Biliary Tract Cancer (BTC) Biliary Tract Diseases Biliary Tract Neoplasms Colonic Diseases Colorectal Cancer (CRC) Colorectal Neoplasms Digestive System Diseases Digestive System Neoplasms Esophageal Cancer (EC) Esophageal Diseases Esophageal Neoplasms Gastric Cancer (GC) Gastrointestinal Diseases Gastrointestinal Neoplasms Head and Neck Neoplasms Head and Neck Squamous Cell Cancer (HNSCC) Intestinal Diseases Intestinal Neoplasms Neoplasms Neoplasms by Site Pancreatic Ductal Adenocarcinoma (PDAC) Rectal Diseases Stomach Diseases Stomach Neoplasms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1

Primary location

Asan Medical Center, Seoul, South Korea

Loading trial locations.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Participants are eligible to be included in the study only if all the following criteria apply:

  • Signed ICF.
  • Participants should be ≥ 18 years (in the US) or ≥19 years (in South Korea) of age at the time of signing the ICF.
  • Histologically and/or cytologically confirmed diagnosis of selected advanced or metastatic solid tumors (relapsed/refractory disease).
  • Selected advanced solid tumors (PDAC, CRC, BTC, HNSCC, EC, and GC) with sufficient target (NTSR1) expression confirmed by SKL35502 imaging as defined in Inclusion Criterion 5, that have progressed following at least one prior line of therapy or for which no other standard therapy with proven clinical benefit is currently available or recommended based on the Investigator's individual risk-benefit assessment. Patients with MSI-H/dMMR CRC must have previously received and progressed on, been intolerant to, or been deemed ineligible for an FDA-approved immune checkpoint inhibitor, unless such therapy is contraindicated.
  • Sufficient target (NTSR1) expression on SKL35502 imaging, defined as uptake above background in at least 1 RECIST v1.1 measurable lesion, with background activity defined in accordance with the Imaging Charter. For study eligibility, NTSR1 positivity will be determined locally at the site by the Investigator based on review by a qualified site nuclear medicine physician/radiologist, as applicable. SKL35502 images and required lesion documentation will also be submitted for central review for dosimetry, biodistribution, lesion alignment, image quality control, and consistency of image analyses across sites. Central review will not replace the site determination of eligibility except in equivocal cases requiring adjudication.
  • Patients with secondary metastasis to the CNS are eligible if they have had all brain metastases resected or have received radiation therapy ending at least 4 weeks prior to C1D1 and they meet all of the following criteria:
  • Residual neurological symptoms ≤ Grade 1
  • No glucocorticoids requirement or patients may be receiving low doses of glucocorticoids (not exceeding a dose equivalent to prednisone 10 mg daily), provided the dose has been stable for at least 2 weeks prior to C1D1
  • Follow-up MRI or CT scan shows no progression of treated lesions and no new lesions.
  • Measurable disease on imaging, as assessed by RECIST v1.1 and/or RANO-BM for brain metastases (Eisenhauer et al, 2009).
  • ECOG performance status ≤ 2.
  • Minimum life expectancy ≥ 12 weeks at enrollment as determined by investigator
  • Willing to follow the contraception requirements as outlined:
  • For females:

WOCBP:

  • Must have a negative serum pregnancy test performed within (≤) 14 days prior to dosing with SKL35502 (where demanded by local regulations; test may be required within 24 hrs. prior to dosing).
  • Compliant with at least 2 highly effective contraceptive methods (e.g., oral contraceptives, IUD, condom with spermicide, etc.) throughout the study and for at least 8 months (i.e., corresponding to 5 half-lives + 6 months) following the last dose of SKL35501.
  • Female patients must not be pregnant or lactating at study screening and during the course of the study and must not become pregnant for at least 8 months (i.e., corresponding to 5 half-lives + 6 months) following the last dose of SKL35501.
  • Abstinence is not considered an adequate contraceptive method on its own.
  • Women of non-childbearing potential:
  • Must be surgically sterile (e.g., tubal occlusion, hysterectomy, bilateral salpingectomy) or postmenopausal (defined as no menstrual cycle for at least 12 consecutive months).
  • For males:
  • Must be surgically sterile, or compliant with a contraceptive method (effective barrier contraception, such as a condom with spermicide) during the study and then for at least 5 months (i.e., corresponding to 5 half-lives + 3 months) after the last dose of SKL35501.
  • Must agree not to donate sperm during the study until 90 days after the last dose of SKL35501.
  • Male patients with female partner(s) of childbearing potential:
  • Female partner must use a highly effective method of contraception (e.g., oral contraceptives, IUD, diaphragm, etc.) during the study and 5 months (i.e., corresponding to 5 half-lives + 3 months) following the male patient's last dose of SKL35501.
  • Male patients with female partner(s) of non-childbearing potential (i.e., postmenopausal or surgically sterile for at least 6 months prior to Screening):
  • No additional contraception method is required.
  • Adequate hematologic and end-organ function, defined based on the following laboratory results obtained within (≤) 14 days prior to C1D1:
  • ANC ≥ 1.5 × 109/L (1500/μL), without G-CSF support. G-CSF may be administered until (>) 14 days prior to C1D1.
  • Platelet counts ≥ 100 × 109/L (100,000/μL) without receiving any thrombopoietin receptor agonists, other therapies for thrombocytopenia or platelet transfusion for ≥ 14 days prior to C1D1.
  • Hemoglobin ≥ 90 g/L (9 g/dL). Patients may be transfused or receive erythropoietic treatment to meet this criterion until (>) 14 days prior to C1D1.
  • AST and ALT ≤ 3 × ULN (≤ 5 × ULN for patients with documented liver metastases).
  • Total bilirubin ≤ 1.5 × ULN (≤ 3 × ULN for patients with Gilbert's syndrome).
  • eGFR ≥ 60 mL/min (multiply the estimate of GFR by individual's BSA (calculated using an appropriate formula) and divide by 1.73 m2).
  • Albumin > 28 g/L

Exclusion criteria

Patients are excluded from the study if any of the following criteria apply:

Medical Conditions:

  • Patients with evidence of hydronephrosis.
  • History of solid tumor malignancy other than the diseases under study, diagnosed within (≤) the last 3 years of study enrollment, excluding adequately treated basal cell carcinoma of the skin, squamous cell carcinoma of the skin, or in situ cervical cancer, in situ breast cancer, in situ prostate cancer (patients must have shown no evidence of active disease for 2 years prior to enrollment).
  • History of ascites or pleural effusion, unless successfully treated, asymptomatic, and not requiring treatment for > 2 months prior to C1D1.
  • History of and/or current cardiovascular events or conditions:
  • History of myocardial infarction, unstable or severe angina, or arterial thrombotic event (such as CVA or TIA) within (≤) 12 months prior to C1D1
  • Current NYHA stage II-IV congestive heart failure
  • Unstable arrhythmia, or history or presence of a clinically significant (in the Investigator's opinion) ECG abnormality
  • Screening QT (QTc) interval (average of triplicate measurements; corrected for heart rate using Fridericia's formula) > 470 msec
  • Uncontrolled hypertension, defined as SBP > 150 mm Hg and/or DBP > 100 mm Hg at screening, despite optimal antihypertensive therapy.
  • Positive tests at screening for the following:
  • HIV: HIV patients on established ART for at least 4 weeks and have a viral load less than 400 copies/mL and CD4+ T-cell counts ≥350 μL may be eligible.
  • HBsAg: Patients with positive HBV test and HBV DNA < 500 copies being treated with antivirals may participate.

i. HBcAb: Patients with a positive HBcAb test followed by a negative HBV DNA test at screening may be enrolled.

ii. HCV antibody test: Patients with a positive HCV antibody test followed by a negative HCV RNA test at screening may be enrolled.

  • Active thrombophlebitis, thromboembolism, hypercoagulability states, bleeding:
  • Patients with a history of DVT may participate if successfully treated, completely resolved, and no treatment has been given for > 2 months.
  • Patients who suffered a thromboembolism > 6 months prior and who are stable on anticoagulation may participate.
  • Uncontrolled diabetes.
  • Chronic severe liver disease or liver cirrhosis.
  • Any active or symptomatic persistent infection (bacterial, viral, or fungal) requiring systemic therapy within (≤) 14 days prior to C1D1.
  • Any psychiatric illness or social situation that would limit compliance with study requirements.
  • Any other significant co-morbidity, disease, metabolic dysfunction, physical examination, or clinical laboratory finding that contraindicates the use of an investigational drug, or may represent an unacceptable risk from treatment complications, or may affect adherence to the study procedures or the interpretation of the results.

Ineligible prior and ongoing treatment requirements:

  • Treatment with previous cancer therapies (including investigational cancer treatment) ≤ 28 days or 5 half-lives prior to C1D1, or radiation therapy within (≤) 4 weeks prior to start of SKL35502 (palliative radiation or stereotactic radiosurgery within (≤) 7 days prior to start of SKL35502). Patients must have recovered from all acute radiotherapy-related toxicities.
  • Prior radiopharmaceutical or radioligand therapy.
  • Patients who are receiving treatment with medications known to prolong the QT/QTc interval.
  • Live, attenuated vaccine within (≤) 28 days prior to C1D1, or anticipation of need for such a vaccine during the course of the study. COVID-19 vaccination is acceptable.
  • Any other therapy that is prohibited during the study. Refer to Section 6.9.1.

Other Exclusion Criteria:

  • Known hypersensitivity to SKL35502 or SKL35501 or any component(s) of SKL35502 or SKL35501.
  • Contraindications to or inability to perform the imaging procedures required in this study.
  • History of drug-induced anaphylactic or other severe hypersensitivity reactions.
  • History of any of the following: drug-induced SCAR; including but not limited to SJS/TEN, or DRESS syndrome), or dose-limiting immune-mediated reactions.
  • Current pregnancy and/or breast-feeding.

Treatment and study plan

SKL35501

Drug

Therapeutic agent that consists of an NTSR1-targeting small molecule linked to alpha emitter 225Ac to induce killing of NTSR1-expressing tumor cells

SKL35502

Diagnostic Test

Imaging agent that consists of an NTSR1-targeting small molecule linked to 111In to detect NTSR1-expressing tumors via SPECT imaging

Primary outcomes

  1. Number of Participants With Treatment-Emergent Adverse Events Following SKL35502 Administration

    Time frame: From the first administration of SKL35502 until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one treatment-emergent adverse event following administration of SKL35502 will be reported. A treatment-emergent adverse event is an adverse event that begins or worsens after the first administration of SKL35502. Adverse-event severity will be assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 6.0. Each participant will be counted once for this outcome regardless of the number of events experienced.

  2. Absorbed Radiation Dose to Prespecified Normal Organs Following SKL35502 Administration

    Time frame: From SKL35502 administration through 7 days after administration.

    Absorbed radiation dose will be estimated for each prespecified normal organ following SKL35502 administration using serial imaging, organ time-activity data, and protocol-defined dosimetry methods. Organ-specific absorbed-dose values will be reported separately using the same protocol-defined absorbed-dose unit.

  3. Absorbed Radiation Dose to Evaluable Tumor Lesions Following SKL35502 Administration

    Time frame: From SKL35502 administration through 7 days after administration.

    Absorbed radiation dose will be estimated for each evaluable tumor lesion following SKL35502 administration using serial imaging, lesion time-activity data, and protocol-defined dosimetry methods. Lesion-specific absorbed-dose values will be reported separately using the same protocol-defined absorbed-dose unit.

  4. Whole-Body Radiation Dose Following SKL35502 Administration

    Time frame: From SKL35502 administration through 7 days after administration.

    The whole-body radiation dose following SKL35502 administration will be estimated using serial imaging and protocol-defined dosimetry methods. One whole-body radiation-dose value will be reported for each evaluable participant using the protocol-defined unit.

  5. Number of Participants With Dose-Limiting Toxicities During Cycle 1 Following the First Dose of SKL35501

    Time frame: From the first administration of SKL35501 through the end of Cycle 1, a period of 6 weeks.

    The number of participants who experience at least one SKL35501-related dose-limiting toxicity during the protocol-defined dose-limiting toxicity assessment period will be reported. Dose-limiting toxicities are protocol-defined hematologic or non-hematologic adverse events occurring during the first treatment cycle. Each participant will be counted once regardless of the number of dose-limiting toxicities experienced.

  6. Lower SKL35501 Administered Activity Selected for the Biologically Active Dose Range for Part B

    Time frame: At completion of Part A dose escalation and backfill, after all Part A participants have completed at least one 6-week treatment cycle.

    The lower SKL35501 administered activity selected for the biologically active dose range will be determined by the Safety Review Committee based on integrated review of dose-limiting toxicities, safety and tolerability beyond the dose-limiting toxicity assessment period, pharmacokinetics, pharmacodynamics, imaging, dosimetry, and preliminary antitumor activity. One lower administered-activity value will be reported in megabecquerels.

  7. Upper SKL35501 Administered Activity Selected for the Biologically Active Dose Range for Part B

    Time frame: At completion of Part A dose escalation and backfill, after all Part A participants have completed at least one 6-week treatment cycle.

    The upper SKL35501 administered activity selected for the biologically active dose range will be determined by the Safety Review Committee based on integrated review of dose-limiting toxicities, safety and tolerability beyond the dose-limiting toxicity assessment period, pharmacokinetics, pharmacodynamics, imaging, dosimetry, and preliminary antitumor activity. One upper administered-activity value will be reported in megabecquerels.

  8. Tumor-to-Background Ratio of SKL35502 Uptake in RECIST Version 1.1 Measurable Tumor Lesions

    Time frame: From SKL35502 administration through 144 hours after administration.

    Tumor-to-background ratio will be calculated as SKL35502 uptake in an anatomically matched RECIST Version 1.1 measurable tumor lesion divided by uptake in the background reference region defined in the Imaging Charter or Imaging Manual. Tumor-to-background ratio values will be summarized separately at each protocol-specified imaging time point.

  9. Number of Participants With at Least One SKL35502-Positive RECIST Version 1.1 Measurable Tumor Lesion

    Time frame: From SKL35502 administration through 144 hours after administration.

    The number of participants with at least one anatomically matched RECIST Version 1.1 measurable tumor lesion demonstrating focal SKL35502 uptake above the Imaging Charter-defined background region will be reported. Positivity will be assessed by a qualified nuclear medicine physician or radiologist using the protocol-defined visual and quantitative imaging criteria.

  10. SKL35502 Imaging Time Point Selected for Tumor Eligibility Assessment

    Time frame: At completion of the Part A SKL35502 imaging review following collection of imaging data through 144 hours after administration.

    The imaging time point selected for tumor eligibility assessment will be determined based on integrated review of tumor visualization, tumor-to-background ratio, normal-tissue uptake, image quality, biodistribution, and operational feasibility. One selected imaging time point will be reported as the number of hours after SKL35502 administration.

  11. Percentage of Participants With Complete Response, Partial Response, or Stable Disease Lasting at Least 4 Months Following SKL35501 Treatment

    Time frame: Tumor assessments will be performed every 8 weeks during the first 6 months and every 12 weeks thereafter, up to 12 months after the last participant's first SKL35501 dose.

    The percentage of efficacy-evaluable participants whose best overall response is complete response or partial response, or whose stable disease lasts for at least 4 months, will be reported. Tumor response will be assessed by the Investigator according to RECIST Version 1.1 and, where applicable, RANO-BM for brain metastases.

  12. Objective Response Rate Following SKL35501 Treatment

    Time frame: Tumor assessments will be performed every 8 weeks during the first 6 months and every 12 weeks thereafter, up to 12 months after the last participant's first SKL35501 dose.

    Objective response rate is the percentage of efficacy-evaluable participants whose best overall response is complete response or partial response, as assessed by the Investigator according to RECIST Version 1.1 and, where applicable, RANO-BM for brain metastases.

  13. Clinical Benefit Rate Following SKL35501 Treatment

    Time frame: Tumor assessments will be performed every 8 weeks during the first 6 months and every 12 weeks thereafter, up to 12 months after the last participant's first SKL35501 dose.

    Clinical benefit rate is the percentage of efficacy-evaluable participants whose best overall response is complete response, partial response, or stable disease, as assessed by the Investigator according to RECIST Version 1.1 and, where applicable, RANO-BM for brain metastases.

  14. Progression-Free Survival Following SKL35501 Treatment

    Time frame: From the first SKL35501 dose until documented disease progression, death, or completion of protocol-defined efficacy follow-up, up to 12 months after the last participant's first SKL35501 dose.

    Progression-free survival is defined as the time from the first administration of SKL35501 to the first documented disease progression, as determined by the Investigator according to RECIST Version 1.1 and, where applicable, RANO-BM for brain metastases, or death from any cause, whichever occurs first.

  15. Time to Disease Progression Following SKL35501 Treatment

    Time frame: From the first SKL35501 dose until documented disease progression or completion of protocol-defined efficacy follow-up, up to 12 months after the last participant's first SKL35501 dose.

    Time to disease progression is defined as the time from the first administration of SKL35501 to the first documented disease progression, as determined by the Investigator according to RECIST Version 1.1 and, where applicable, RANO-BM for brain metastases.

  16. Overall Survival Following SKL35501 Treatment

    Time frame: From the first SKL35501 dose until death, loss to follow-up, withdrawal of consent, or completion of protocol-defined survival follow-up, up to 12 months after the last participant's first SKL35501 dose.

    Overall survival is defined as the time from the first administration of SKL35501 to death from any cause.

Secondary outcomes

  1. Number of Participants With Grade 3 or Higher Treatment-Emergent Adverse Events Following SKL35502 Administration

    Time frame: From the first administration of SKL35502 until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one Grade 3 or higher treatment-emergent adverse event following administration of SKL35502 will be reported. Severity will be assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 6.0. Each participant will be counted once regardless of the number of events experienced.

  2. Number of Participants With Serious Adverse Events Following SKL35502 Administration

    Time frame: From the first administration of SKL35502 until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one serious adverse event following administration of SKL35502 will be reported. Each participant will be counted once regardless of the number of serious adverse events experienced.

  3. Number of Participants With Adverse Events of Special Interest Following SKL35502 Administration

    Time frame: From the first administration of SKL35502 until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one protocol-defined adverse event of special interest following administration of SKL35502 will be reported. Each participant will be counted once regardless of the number of adverse events of special interest experienced.

  4. Number of Participants With Clinically Significant 12-Lead Electrocardiogram Abnormalities Following SKL35502 Administration

    Time frame: From baseline until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one clinically significant abnormality or clinically significant change from baseline in heart rate, cardiac rhythm, PR interval, QRS duration, QT interval, or QT interval corrected using Fridericia's formula will be reported. Clinical significance will be determined by the Investigator. Each participant will be counted once for this outcome.

  5. Number of Participants With Clinically Significant Vital-Sign Abnormalities Following SKL35502 Administration

    Time frame: From baseline until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one protocol-defined clinically significant vital-sign abnormality or clinically significant change from baseline following SKL35502 administration will be reported. Each participant will be counted once regardless of the number of vital-sign abnormalities experienced.

  6. Number of Participants With Clinically Significant Physical Examination Findings Following SKL35502 Administration

    Time frame: From baseline until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one clinically significant new or worsened physical examination finding following SKL35502 administration will be reported. Clinical significance will be determined by the Investigator. Each participant will be counted once for this outcome.

  7. Number of Participants With Clinically Significant Safety Laboratory Abnormalities Following SKL35502 Administration

    Time frame: From baseline until initiation of SKL35501, 15 days after the last administration of SKL35502, or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one clinically significant hematology or clinical chemistry laboratory abnormality or clinically significant change from baseline following SKL35502 administration will be reported. Laboratory abnormalities will be graded using the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 6.0, where applicable. Each participant will be counted once for this outcome.

  8. Total Radioactivity Concentration in Whole Blood Following SKL35502 Administration

    Time frame: From predose through 144 hours after SKL35502 administration.

    Total radioactivity concentration in whole blood will be measured and summarized separately at each protocol-specified collection time following SKL35502 administration.

  9. Total Radioactivity Concentration in Plasma Following SKL35502 Administration

    Time frame: From predose through 144 hours after SKL35502 administration.

    Total radioactivity concentration in plasma will be measured and summarized separately at each protocol-specified collection time following SKL35502 administration.

  10. Total Radioactivity Concentration in Urine Following SKL35502 Administration

    Time frame: From predose through 72 hours after SKL35502 administration.

    Total radioactivity concentration in urine will be measured and summarized separately for each protocol-specified urine collection interval following SKL35502 administration.

  11. Correlation Coefficient Between SKL35502 Tumor-to-Background Ratio and Tumor NTSR1 Expression

    Time frame: After completion of the corresponding tumor tissue assessment and SKL35502 imaging assessments, with imaging performed through 144 hours after SKL35502 administration.

    SKL35502 tumor uptake will be represented by the tumor-to-background ratio for an evaluable tumor lesion. Tumor NTSR1 expression will be represented by the protocol-specified quantitative result obtained from corresponding tumor tissue when available. One protocol-specified correlation coefficient describing the association between tumor-to-background ratio and tumor NTSR1 expression will be reported.

  12. Number of Participants With Treatment-Emergent Adverse Events Following SKL35501 Administration

    Time frame: From the first administration of SKL35501 through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one treatment-emergent adverse event following administration of SKL35501 will be reported. A treatment-emergent adverse event is an adverse event that begins or worsens after the first administration of SKL35501. Severity will be assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 6.0. Each participant will be counted once for this outcome. Results will be summarized by applicable Part A dose cohort and Part B dose group, including participants treated at the biologically active dose range.

  13. Number of Participants With Grade 3 or Higher Treatment-Emergent Adverse Events Following SKL35501 Administration

    Time frame: From the first administration of SKL35501 through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one Grade 3 or higher treatment-emergent adverse event following administration of SKL35501 will be reported. Severity will be assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 6.0. Each participant will be counted once regardless of the number of events experienced.

  14. Number of Participants With Serious Adverse Events Following SKL35501 Administration

    Time frame: From the first administration of SKL35501 through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one serious adverse event following administration of SKL35501 will be reported. Each participant will be counted once regardless of the number of serious adverse events experienced.

  15. Number of Participants With Adverse Events of Special Interest Following SKL35501 Administration

    Time frame: From the first administration of SKL35501 through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one protocol-defined adverse event of special interest following administration of SKL35501 will be reported. Each participant will be counted once regardless of the number of adverse events of special interest experienced.

  16. Number of Participants With Clinically Significant 12-Lead Electrocardiogram Abnormalities Following SKL35501 Administration

    Time frame: From baseline through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one clinically significant abnormality or clinically significant change from baseline in heart rate, cardiac rhythm, PR interval, QRS duration, QT interval, or QT interval corrected using Fridericia's formula will be reported. Clinical significance will be determined by the Investigator. Each participant will be counted once for this outcome.

  17. Number of Participants With Clinically Significant Vital-Sign Abnormalities Following SKL35501 Administration

    Time frame: From baseline through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one protocol-defined clinically significant vital-sign abnormality or clinically significant change from baseline following SKL35501 administration will be reported. Each participant will be counted once regardless of the number of vital-sign abnormalities experienced.

  18. Number of Participants With Clinically Significant Physical Examination Findings Following SKL35501 Administration

    Time frame: From baseline through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one clinically significant new or worsened physical examination finding following SKL35501 administration will be reported. Clinical significance will be determined by the Investigator. Each participant will be counted once for this outcome.

  19. Number of Participants With Clinically Significant Safety Laboratory Abnormalities Following SKL35501 Administration

    Time frame: From baseline through 50 days after the last administration of SKL35501 or initiation of a new antitumor therapy, whichever occurs first.

    The number of participants with at least one clinically significant hematology or clinical chemistry laboratory abnormality or clinically significant change from baseline following SKL35501 administration will be reported. Laboratory abnormalities will be graded using the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 6.0, where applicable. Each participant will be counted once for this outcome.

  20. Total Radioactivity Concentration in Whole Blood Following SKL35501 Administration

    Time frame: From predose through 168 hours after SKL35501 administration in Cycles 1 and 3, with additional samples collected on Day 1 of Cycles 2 and 4. Each treatment cycle is 6 weeks.

    Total radioactivity concentration in whole blood will be measured and summarized separately at each protocol-specified collection time following SKL35501 administration.

  21. Total Radioactivity Concentration in Plasma Following SKL35501 Administration

    Time frame: From predose through 168 hours after SKL35501 administration in Cycles 1 and 3, with additional samples collected on Day 1 of Cycles 2 and 4. Each treatment cycle is 6 weeks.

    Total radioactivity concentration in plasma will be measured and summarized separately at each protocol-specified collection time following SKL35501 administration.

  22. Total Radioactivity Concentration in Urine Following SKL35501 Administration

    Time frame: From predose through 72 hours after the Cycle 1 SKL35501 dose. Cycle 1 is 6 weeks.

    Total radioactivity concentration in urine will be measured and summarized separately for each protocol-specified urine collection interval following the Cycle 1 administration of SKL35501.

  23. Duration of Response Following SKL35501 Treatment

    Time frame: From the first documented complete response or partial response until documented disease progression, death, or completion of protocol-defined efficacy follow-up, up to 12 months after the last participant's first SKL35501 dose.

    For participants whose best overall response is complete response or partial response, duration of response is defined as the time from the first documented complete response or partial response to the first documented disease progression, as determined by the Investigator according to RECIST Version 1.1 and, where applicable, RANO-BM for brain metastases, or death from any cause, whichever occurs first.

  24. Absorbed Radiation Dose to Prespecified Normal Organs Following SKL35501 Administration

    Time frame: From the first SKL35501 dose through 168 hours after SKL35501 administration in Cycles 1 and 3. Each treatment cycle is 6 weeks.

    Absorbed radiation dose will be estimated for each prespecified normal organ, including high-uptake and critical tissues such as the kidneys, liver, red marrow, and spleen, using serial imaging, organ time-activity data, and protocol-defined dosimetry methods. Organ-specific values will be reported separately using the same protocol-defined absorbed-dose unit.

  25. Absorbed Radiation Dose to Evaluable Tumor Lesions Following SKL35501 Administration

    Time frame: From the first SKL35501 dose through 168 hours after SKL35501 administration in Cycles 1 and 3. Each treatment cycle is 6 weeks.

    Absorbed radiation dose will be estimated for each evaluable tumor lesion using serial imaging, lesion time-activity data, and protocol-defined dosimetry methods. Lesion-specific absorbed-dose values will be reported separately using the same protocol-defined absorbed-dose unit.

  26. Cumulative Absorbed Radiation Dose to Prespecified Normal Organs Across SKL35501 Treatment Cycles

    Time frame: From the first SKL35501 dose through completion of up to 4 treatment cycles, up to approximately 24 weeks. Each treatment cycle is 6 weeks.

    The cumulative absorbed radiation dose to each prespecified normal organ will be estimated across all SKL35501 treatment cycles received by the participant using protocol-defined dosimetry methods. Organ-specific cumulative absorbed-dose values will be reported separately using the same protocol-defined absorbed-dose unit.

  27. Maximum Absorbed Radiation Dose Among Prespecified Normal Organs Following SKL35501 Administration

    Time frame: From the first SKL35501 dose through completion of dosimetry assessments in Cycles 1 and 3, with serial imaging through 168 hours after each dose. Each treatment cycle is 6 weeks.

    For each evaluable participant, the highest absorbed radiation dose among the prespecified normal organs will be determined from the organ-specific dosimetry results. One maximum normal-organ absorbed-dose value will be reported for each participant using the protocol-defined absorbed-dose unit.

Study contacts

Contact information is provided by the study sponsor or research team.

Ashley Villa

CONTACT

[email protected]

240-448-6111

Sponsors and collaborators

Lead sponsor

SK Life Science, Inc.

Industry

Registry information

Official study title

A Phase 1 Theranostic Study to Investigate Safety, Tolerability, Pharmacokinetics, and Efficacy of SKL35501, an Alpha-Emitting Radiopharmaceutical Targeting NTSR1, With SKL35502 as Companion Imaging Agent in Adult Patients With Selected Advanced Solid Tumors

Important dates

Study start
2026
Primary completion
2030
Study completion
2030
First posted
Sep 10, 2026
Registry last updated
Sep 10, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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