18 and older, any sex, with Advanced Solid Tumors. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Number of Participants Who Experienced a Treatment-related Adverse Event (AE) or Laboratory Abnormality by Severity Graded According to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) Version 4.03 CriteriaPrimary· Up to 90 days post last injection (Up to approximately 192 days)
An AE was defined as any untoward medical occurrence in a study participant administered study treatment which did not necessarily have a causal relationship with this treatment. Treatment-related was defined as having a "Possible" or "Related" relationship to study treatment, as assessed by the Investigator. Severity of AE referred to the extent to which an AE affected the participants daily activities as assessed by the Investigator and was based on NCI CTCAE grades: Grade 1 (Mild); Grade 2 (Moderate); Grade 3 (Severe or medically significant but not immediately life-threatening); Grade 4 (L
Grade 1
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
Group A: MK-4621 0.4 mg
2
Group A: MK-4621 0.6 mg
2
Group A: MK-4621 0.8 mg
3
Grade 2
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
1
Group A: MK-4621 0.6 mg
1
Group A: MK-4621 0.8 mg
2
Grade 3
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
1
Grade 4
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Grade 5
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Number of Participants Who Experienced a Serious Adverse Event (SAE)Primary· Up to 90 days post last injection (Up to approximately 192 days)
A SAE was defined as any AE, regardless of dose, causality or expectedness, that:
* Resulted in death;
* Was life-threatening;
* Required inpatient hospitalization or prolonged existing inpatient hospitalization;
* Resulted in persistent or significant incapacity or disability;
* Was a congenital anomaly or birth defect; or
* Was any other medically important event.
Group
Value
95% CI
Group A: MK-4621 0.2 mg
2
Group A: MK-4621 0.4 mg
2
Group A: MK-4621 0.6 mg
1
Group A: MK-4621 0.8 mg
3
Number of Participants Who Discontinued Study Treatment Due to a Treatment-related Adverse Event (AE)Primary· Up to last injection (Up to approximately 102 days)
An AE was defined as any untoward medical occurrence in a study participant administered a study treatment which did not necessarily have a causal relationship with this treatment. Treatment-related was defined as having a "Possible" or "Related" relationship to study treatment, as assessed by the Investigator. The number of participants who discontinued study treatment due to a treatment-related AE is presented.
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Number of Participants Who Experienced a Dose-limiting Toxicity (DLT) by Severity Graded According to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) Version 4.03 CriteriaPrimary· Cycle 1 (Up to approximately 28 days); Each cycle was 28 days.
DLTs were assessed during the first treatment cycle (28 days) \& were defined as any drug-related toxicity that occurred during the 28-day DLT period and included:
* Non-hematologic toxicity grade ≥3 (except diarrhea, nausea, and vomiting unless lasting \>3 days despite optimal supportive care);
* Confirmed (with a second measurement after 24 hours) non-hematologic appropriately graded laboratory findings of Grade ≥3 that were ≤ Grade 1 at baseline;
* Hematologic toxicity:
* Grade 4 neutropenia ≥5 days, or Grade 3 neutropenia with fever (fever is \>38.4ºC)
* Grade 4 thrombocytopenia, or
Grade 1
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Grade 2
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Grade 3
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Grade 4
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Grade 5
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
Group A: MK-4621 0.4 mg
0
Group A: MK-4621 0.6 mg
0
Group A: MK-4621 0.8 mg
0
Objective Response Rate as Evaluated Radiologically Using Immune-related Response Evaluation Criteria in Solid Tumors (irRECIST)Secondary· Up to 60 days post last injection (Up to approximately 162 days)
ORR was defined as the percentage of participants who had a Complete Response (CR) or a Partial Response. Per irRECIST, CR (irCR) was defined as the complete disappearance of all measurable and non-measurable lesions. Lymph nodes must also have decreased to \<0 mm in short axis. And, per irRECIST, Partial Response (irPR) was defined as a decrease of ≥30% in total measured tumor burden (TMTB) relative to baseline. For this study, irRECIST was modified to follow a maximum of 10 target lesions and a maximum of 5 target lesions per organ. The percentage of participants who experienced an irCR or i
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0
0.0 – 70.8
Group A: MK-4621 0.4 mg
0
0.0 – 70.8
Group A: MK-4621 0.6 mg
0
0.0 – 70.8
Group A: MK-4621 0.8 mg
0
0.0 – 45.9
Mean Fold Change From Baseline in Plasma Cytokine Release by Cytokine Type: Day 1 (6 Hours Post Injection)Secondary· Baseline and Cycle 1 Day 1 (6 hours post injection) (Up to 1 day); Each cycle was 28 days.
Blood samples were collected at various time points for the analysis of mean fold change from baseline in cytokine release for selected cytokines (Interleukin-6 \[IL-6\] and tumor necrosis factor-alpha \[TNF-a\]) in plasma.
IL-6
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
± 0
Group A: MK-4621 0.4 mg
1.95
± 1.64
Group A: MK-4621 0.6 mg
2.71
± 2.34
Group A: MK-4621 0.8 mg
2.52
± 3.14
TNF-a
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
± 0
Group A: MK-4621 0.4 mg
1
± 0
Group A: MK-4621 0.6 mg
1
± 0.6
Group A: MK-4621 0.8 mg
0.89
± 0.28
Mean Fold Change From Baseline in Plasma Cytokine Release by Cytokine Type: Day 1 (24 Hours Post Injection)Secondary· Baseline and Cycle 1 Day 1 (24 hours post injection) (Up to 2 days); Each cycle was 28 days.
Blood samples were collected at various time points for the analysis of mean fold change from baseline in cytokine release for selected cytokines (Interleukin-6 \[IL-6\] and tumor necrosis factor-alpha \[TNF-a\]) in plasma.
IL-6
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
± 0
Group A: MK-4621 0.4 mg
1.27
± 0.46
Group A: MK-4621 0.6 mg
1.14
± 0.3
Group A: MK-4621 0.8 mg
1.68
± 0.97
TNF-a
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
± 0
Group A: MK-4621 0.4 mg
1
± 0
Group A: MK-4621 0.6 mg
1.48
± 1.44
Group A: MK-4621 0.8 mg
0.89
± 0.28
Mean Fold Change From Baseline in Plasma Cytokine Release by Cytokine Type: Day 25 (6 Hours Post Injection)Secondary· Baseline and Cycle 1 Day 25 (6 hours post injection) (Up to 25 days); Each cycle was 28 days.
Blood samples were collected at various time points for the analysis of mean fold change from baseline in cytokine release for selected cytokines (Interleukin-6 \[IL-6\] and tumor necrosis factor-alpha \[TNF-a\]) in plasma.
IL-6
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0.95
± 0.08
Group A: MK-4621 0.4 mg
2
± 1.11
Group A: MK-4621 0.6 mg
1.02
± 0.31
Group A: MK-4621 0.8 mg
1.5
± 0.61
TNF-a
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
± 0
Group A: MK-4621 0.4 mg
1
± 0
Group A: MK-4621 0.6 mg
0.77
± 0.21
Group A: MK-4621 0.8 mg
0.77
± 0.29
Mean Fold Change From Baseline in Plasma Cytokine Release by Cytokine Type: Day 25 (24 Hours Post Injection)Secondary· Baseline and Cycle 1 Day 25 (24 hours post injection) (Up to 26 days); Each cycle was 28 days.
Blood samples were collected at various time points for the analysis of mean fold change from baseline in cytokine release for selected cytokines (Interleukin-6 \[IL-6\] and tumor necrosis factor-alpha \[TNF-a\]) in plasma.
IL-6
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1.52
± 0.9
Group A: MK-4621 0.4 mg
1
± 0
Group A: MK-4621 0.6 mg
0.99
± 0.1
Group A: MK-4621 0.8 mg
0.89
± 0.19
TNF-a
Group
Value
95% CI
Group A: MK-4621 0.2 mg
1
± 0
Group A: MK-4621 0.4 mg
1
± 0
Group A: MK-4621 0.6 mg
1.02
± 0.63
Group A: MK-4621 0.8 mg
0.88
± 0.32
Area Under the Concentration-Time Curve From Start of Dosing to Last Observed Concentration Above Limit of Quantitation (AUC0-t) of MK-4621: Day 1Secondary· Cycle 1 Day 1: Predose, 5 and 30 minutes, 2, 4, 6 and 24 hours post dose (Up to 2 days); Each cycle was 28 days.
Blood samples were collected at various time points during Cycle 1 for the determination of MK-4621 AUC0-t on Day 1, which was defined as the AUC from the start time of dosing to the time of the last observed concentration above the limit of quantitation (LOQ).
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0.00
± 0.00
Group A: MK-4621 0.4 mg
0.174
± 0.157
Group A: MK-4621 0.6 mg
0.0360
± 0.0623
Group A: MK-4621 0.8 mg
1.87
± 4.55
Area Under the Concentration-Time Curve From Start of Dosing to Last Observed Concentration Above Limit of Quantitation (AUC0-t) of MK-4621: Day 25Secondary· Cycle 1 Day 25: Predose, 5 and 30 minutes, 2, 4, 6 and 24 hours post dose (Up to 26 days); Each cycle was 28 days.
Blood samples were collected at various time points during Cycle 1 for the determination of MK-4621 AUC0-t on Day 25, which was defined as the AUC from the start time of dosing to the time of the last observed concentration above the limit of quantitation (LOQ).
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0.00
± 0.00
Group A: MK-4621 0.4 mg
1.07
± 0.767
Group A: MK-4621 0.6 mg
0.099
± 0.172
Group A: MK-4621 0.8 mg
0.156
± 0.350
Maximum Plasma Concentration (Cmax) of MK-4621: Day 1Secondary· Cycle 1 Day 1: Predose, 5 and 30 minutes, 2, 4, 6 and 24 hours post dose (Up to 2 days); Each cycle was 28 days.
Blood samples were collected at various time points during Cycle 1 for the determination of MK-4621 Cmax on Day 1.
Group
Value
95% CI
Group A: MK-4621 0.2 mg
0.00
± 0.00
Group A: MK-4621 0.4 mg
4.18
± 3.76
Group A: MK-4621 0.6 mg
0.863
± 1.50
Group A: MK-4621 0.8 mg
9.24
± 21.9
Adverse events — posted to ClinicalTrials.gov
Time frame: From first dose through up to 90 days after last dose (Up to approximately 192 days).
Reporting threshold: 5%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
Group A: MK-4621 0.2 mg
Serious: 2/3 (67%)
Deaths: 2/3
Group A: MK-4621 0.4 mg
Serious: 2/3 (67%)
Deaths: 0/3
Group A: MK-4621 0.6 mg
Serious: 1/3 (33%)
Deaths: 1/3
Group A: MK-4621 0.8 mg
Serious: 3/6 (50%)
Deaths: 1/6
Serious adverse events (10 terms)
Reaction
System
Group A: MK-4621 0.2 mg
Group A: MK-4621 0.4 mg
Group A: MK-4621 0.6 mg
Group A: MK-4621 0.8 mg
Disease progression
General disorders
—
—
—
—
Pyrexia
General disorders
—
—
—
—
Device related infection
Infections and infestations
—
—
—
—
Pneumonia
Infections and infestations
—
—
—
—
Soft tissue infection
Infections and infestations
—
—
—
—
Neoplasm progression
Neoplasms benign, malignant and unspecified (incl cysts and polyps)
This is a Phase I/II multicenter, first-in-human open-label, dose escalation study to evaluate the safety, tolerability, and anti-tumor activity of intratumoral (IT)/intralesional (IL) injections of MK-4621 (RGT100) in adult participants with selected advanced or recurrent tumors.
Publications & conference data
8 peer-reviewed publications reference this trial (live from Europe PMC):
NCT03739138 — Intratumoral/Intralesional Administration of MK-4621/JetPEI™ With or Without Pembrolizumab in Participants With Advanced
· Phase 1
· terminated
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Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Merck Sharp & Dohme LLC
Last refreshed: 30 July 2019
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT03065023.