A Phase 1/2 interventional study of NKTR-255 and Cetuximab in Head and Neck Squamous Cell Carcinoma and Colorectal Cancer, sponsored by Nektar Therapeutics. Completed at 6 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2025-06-08.
Sponsored by Nektar Therapeutics · Phase 1/2, Interventional, and Treatment
This is a Phase 1b/2, open-label multicenter study evaluating NKTR-255 as a monotherapy and together with cetuximab in patients with head and neck squamous cell carcinoma (HNSCC) and colorectal carcinoma (CRC).
NKTR-255 is a cytokine that is designed to regulate T and natural killer cell activation, proliferation and promote their anti-tumor effects.
In the dose escalation (Phase 1/b) phase patients with HNSCC or CRC will be treated with ascending doses of NKTR-255 in combination with cetuximab, until the maximum tolerated dose (MTD) and/or the recommended Phase 2 dose (RP2D) is reached.
2,018 studies on the registry are indexed under Squamous Cell Carcinoma of Head and Neck; 573 are open to participants now.
This study's enrollment of 25 is below the median of 48 across 1,653 interventional studies indexed under Squamous Cell Carcinoma of Head and Neck.
Browse Squamous Cell Carcinoma of Head and Neck studies →Nektar Therapeutics is the lead sponsor of 39 studies on the registry; 2 are open to participants now.
Of its 22 completed or terminated interventional studies of FDA-regulated products, 13 (59%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
HNSCC:
CRC:
Key Exclusion Criteria:
NOTE: Other protocol defined inclusion/exclusion criteria may apply
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
PD-1, PD-L1 and checkpoint inhibitors
PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.
PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Establish RP2D, of NKTR-255 with cetuximab.
Drug: NKTR-255 · Drug: Cetuximab
Incidence of Treatment-Emergent Adverse Events (TEAE) and Serious Adverse Events (SAE) of NKTR-255 in Combination With Cetuximab in R/R HNSCC or CRC for Phase 1b Dose Escalation
Safety and tolerability of NKTR-255 in combination with cetuximab as evaluated by dose limiting toxicities, incidence of drug-related Adverse Events (AEs), SAEs, and AEs leading to discontinuation, deaths, and clinical laboratory abnormalities per CTCAE 5.0
Time frame: 60 days after the last dose of study treatment, up to an average of 6 months.
The Maximum Tolerated Dose (MTD) and/or Recommended Phase 2 Dose (RP2D) of NKTR-255 in Combination With Cetuximab in R/R HNSCC or CRC for Phase 1b Dose Escalation
To define the MTD and/or RP2D of NKTR-255 in combination with cetuximab in R/R HNSCC or CRC for Phase 1b Dose Escalation
Time frame: Up to 21 days
| Milestone | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab |
|---|---|---|---|---|
| Started | 8 | 8 | 6 | 3 |
| Number of participants who were included in the "safety population" analysis. | 7 | 7 | 6 | 3 |
| Completed | 0 | 1 | 0 | 0 |
| Not completed | 8 | 7 | 6 | 3 |
| Withdrew: Progressive disease | 3 | 0 | 4 | 1 |
| Withdrew: Death | 2 | 4 | 1 | 0 |
| Withdrew: Withdrawal by subject | 0 | 2 | 0 | 0 |
| Withdrew: Lost to follow-up | 1 | 0 | 0 | 0 |
| Withdrew: Sponsor request | 2 | 1 | 1 | 2 |
Safety and tolerability of NKTR-255 in combination with cetuximab as evaluated by dose limiting toxicities, incidence of drug-related Adverse Events (AEs), SAEs, and AEs leading to discontinuation, deaths, and clinical laboratory abnormalities per CTCAE 5.0
| Participants | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab |
|---|---|---|---|---|
| Patients with dose limiting toxicities (DLTs): Infusion related reaction | 0 | 1 | 0 | 0 |
| Patients With at Least one TEAE | 7 | 7 | 6 | 2 |
| Patients With at Least one TEAE Related to NKTR-255 | 5 | 7 | 5 | 2 |
| Patients With at Least one Serious TEAE | 2 | 2 | 5 | 1 |
| Patients With at Least one Serious TEAE Related to NKTR-255 | 0 | 1 | 0 | 1 |
| Patients With at Least one TEAE Leading to Death | 0 | 0 | 0 | 0 |
| Patients With at Least one TEAE Related to NKTR-255 Leading to Death | 0 | 0 | 0 | 0 |
| Patients With at Least one TEAE Leading to NKTR-255 Discontinuation | 0 | 2 | 0 | 0 |
| Patients With at Least one TEAE Leading to NKTR-255 Delay, Reduction, or Interruption | 2 | 0 | 2 | 0 |
To define the MTD and/or RP2D of NKTR-255 in combination with cetuximab in R/R HNSCC or CRC for Phase 1b Dose Escalation
| µg/kg | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab |
|---|---|---|---|---|
| The Maximum Tolerated Dose (MTD) and/or Recommended Phase 2 Dose (RP2D) of NKTR-255 in Combination With Cetuximab in R/R HNSCC or CRC for Phase 1b Dose Escalation | NA | NA | NA | NA |
Collected over Through study completion, up to 6 months.. Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | 2/8 (25%) | 2/7 (28.6%) | 7/7 (100%) |
| Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | 4/8 (50%) | 2/7 (28.6%) | 7/7 (100%) |
| Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | 1/6 (16.7%) | 5/6 (83.3%) | 6/6 (100%) |
| Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | 1/3 (33.3%) | 1/3 (33.3%) | 2/3 (66.7%) |
| Event | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab |
|---|---|---|---|---|
| Cytokine release syndromeImmune system disorders | 0/7 | 0/7 | 0/6 | 1/3 |
| CellulitisInfections and infestations | 0/7 | 0/7 | 1/6 | 0/3 |
| Lung infectionInfections and infestations | 0/7 | 0/7 | 1/6 | 0/3 |
| SepsisInfections and infestations | 0/7 | 0/7 | 1/6 | 0/3 |
| Urinary tract infectionInfections and infestations | 0/7 | 0/7 | 1/6 | 0/3 |
| SyncopeNervous system disorders | 0/7 | 0/7 | 1/6 | 0/3 |
| Urinary tract obstructionRenal and urinary disorders | 0/7 | 0/7 | 1/6 | 0/3 |
| PneumoniaInfections and infestations | 0/7 | 0/7 | 1/6 | 0/3 |
| Small intestinal obstructionGastrointestinal disorders | 1/7 | 0/7 | 0/6 | 0/3 |
| AstheniaGeneral disorders | 1/7 | 0/7 | 0/6 | 0/3 |
| Event | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab |
|---|---|---|---|---|
| Infusion related reactionInjury, poisoning and procedural complications | 3/7 | 6/7 | 1/6 | 0/3 |
| Dermatitis acneiformSkin and subcutaneous tissue disorders | 5/7 | 4/7 | 2/6 | 1/3 |
| HypokalaemiaMetabolism and nutrition disorders | 1/7 | 0/7 | 3/6 | 0/3 |
| Rash maculo-papularSkin and subcutaneous tissue disorders | 1/7 | 0/7 | 1/6 | 1/3 |
| ChillsGeneral disorders | 1/7 | 1/7 | 2/6 | 1/3 |
| Influenza like illnessGeneral disorders | 0/7 | 1/7 | 1/6 | 1/3 |
| NauseaGastrointestinal disorders | 1/7 | 0/7 | 2/6 | 1/3 |
| DiarrhoeaGastrointestinal disorders | 0/7 | 0/7 | 2/6 | 0/3 |
| VomitingGastrointestinal disorders | 0/7 | 0/7 | 1/6 | 1/3 |
| HypomagnesaemiaMetabolism and nutrition disorders | 1/7 | 0/7 | 2/6 | 0/3 |
Only 23 participants were dosed with NKTR-255 (7 in Level 1, 7 in Level 2, 6 in Level 3, 3 in Level 4) and are included in the Safety Population analysis used for the remainder of results data.
| Age, Continuous(years) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| Mean | 60.7 ± 7.3 | 56.9 ± 11.44 | 60.7 ± 18.02 | 59.0 ± 11.00 | 59.3 ± 11.75 |
| Age, Customized(participants) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| <65 | 5 | 4 | 3 | 2 | 14 |
| >=65 and <75 | 2 | 3 | 2 | 1 | 8 |
| >=75 and <85 | 0 | 0 | 1 | 0 | 1 |
| >=85 | 0 | 0 | 0 | 0 | 0 |
| Sex: Female, Male(Participants) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| Female | 0 | 2 | 3 | 1 | 6 |
| Male | 7 | 5 | 3 | 2 | 17 |
| Race/Ethnicity, Customized(Participants) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| Hispanic or Latino | 1 | 1 | 2 | 0 | 4 |
| Not Hispanic or Latino | 5 | 6 | 4 | 3 | 18 |
| Not Reported | 1 | 0 | 0 | 0 | 1 |
| Unknown | 0 | 0 | 0 | 0 | 0 |
| Race/Ethnicity, Customized(Participants) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| American Indian or Alaska Native | 0 | 0 | 0 | 0 | 0 |
| Asian | 0 | 0 | 0 | 1 | 1 |
| Black or African American | 1 | 1 | 0 | 0 | 2 |
| Native Hawaiian or Other Pacific Islander | 0 | 0 | 0 | 0 | 0 |
| White | 4 | 5 | 5 | 1 | 15 |
| Unknown | 1 | 0 | 1 | 0 | 2 |
| Not Reported | 1 | 1 | 0 | 1 | 3 |
| Eastern Cooperative Oncology Group (ECOG) Performance Status(Participants) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| ECOG PS 0 | 2 | 4 | 3 | 1 | 10 |
| ECOG PS 1 | 5 | 3 | 3 | 2 | 13 |
| Height(centimeter) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| Mean | 176.69 ± 6.370 | 171.78 ± 7.202 | 167.90 ± 14.675 | 168.54 ± 3.062 | 171.76 ± 9.635 |
| Weight(kg) | Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab | Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab | Total |
|---|---|---|---|---|---|
| Mean | 91.77 ± 14.415 | 84.20 ± 14.359 | 87.46 ± 44.884 | 70.98 ± 17.727 | 85.63 ± 25.341 |
1 further baseline measures are reported on the registry.
PDFs hosted by the registry, ClinicalTrials.gov.
This study is completed, as verified in May 2025. You cannot join it, but the record below documents what was studied.
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Studies of the drug tested here: NKTR-255
Squamous Cell Carcinoma of Head and Neck →