ClinicalTrials.gg
CompletedNCT04616196Updated Jun 8, 2025Results posted

Study of NKTR 255 in Combination With Cetuximab in Solid Tumors

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

Phase
Phase 1/2
Study type
Interventional
Enrollment
25
Allocation
Not applicable
Ages
18 Years and older
Sex
All
01

Study summary

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).

Read the detailed description

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.

02

Conditions studied

  • Head and Neck Squamous Cell Carcinoma
  • Colorectal Cancer

Keywords

  • HNSCC
  • Head and Neck Squamous Cell Carcinoma
  • CRC
  • Colorectal Cancer
  • NKTR-255
  • Cetuximab
  • Erbitux®
03

In context

Squamous Cell Carcinoma of Head and Neck

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 →

Lead sponsor

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.

04

Who can participate

Ages eligible
18 Years and older
Sexes eligible
All
Accepts healthy volunteers
No

Eligibility criteria

Key Inclusion Criteria:

  • confirmed diagnosis of a locally advanced or HNSCC or CRC.
  • > 12 weeks as determined by the Investigator.
  • (ECOG) performance status 0 or 1.
  • per 1.1.

HNSCC:

  • Progression on any first or platinum-based chemotherapy and/or or programmed death-ligand 1 antibody.

CRC:

  • Patients must have received or were intolerant to at least 2 prior cancer therapy regimens administered for metastatic disease.

Key Exclusion Criteria:

  • Use of an agent or an investigational device within 28 days before administration of first dose of study drug(s)
  • Prior surgery or radiotherapy within 14 days of initiating study drug(s)
  • Evidence of interstitial lung disease or active, noninfectious pneumonitis; active infection requiring systemic therapy within 7 days prior to dosing
  • Patients who have been previously treated with IL-2 or IL-15
  • Known Grade 3 or 4 reaction to cetuximab, history of allergy to red meat or tick bites, or history of positive test results for immunoglobulin E antibodies against cetuximab
  • Patients who have an active, known, or suspected disease

NOTE: Other protocol defined inclusion/exclusion criteria may apply

Terms in these criteria, in plain language(12)

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.

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.

Metastases

Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.

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.

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.

0
Fully active, no restrictions.
1
Limited in strenuous activity, but walking and able to do light work, such as housework or office work.
2
Walking and able to look after yourself, but unable to work; up and about more than half of waking hours.
3
Able to look after yourself only in part; in bed or a chair more than half of waking hours.
4
Unable to look after yourself at all; in bed or a chair all day.

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.

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.

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.

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.

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.

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.

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.

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.

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.

05

Study design

Phase
Phase 1 / Phase 2
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Sequential assignment
Masking
None (open label)
Enrollment
25 participants (actual)

Study arms

  • Experimental
    Dose Escalation of NKTR-255 with Cetuximab

    Establish RP2D, of NKTR-255 with cetuximab.

    Drug: NKTR-255 · Drug: Cetuximab

Interventions

  • NKTR-255 IV every 21 days

  • Cetuximab will be given at specified doses on specified days

    Also known as: Erbitux®

06

What researchers measure

Primary outcomes

  1. 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.

  2. 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

07

Results

Posted Jun 8, 2025

Participant flow

Participant flow — Overall Study
MilestoneDose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab
Started8863
Number of participants who were included in the "safety population" analysis.7763
Completed0100
Not completed8763
Withdrew: Progressive disease3041
Withdrew: Death2410
Withdrew: Withdrawal by subject0200
Withdrew: Lost to follow-up1000
Withdrew: Sponsor request2112

Outcome measures

PrimaryIncidence 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.
Reported as:
Count of participants · Participants
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
ParticipantsDose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab
Patients with dose limiting toxicities (DLTs): Infusion related reaction0100
Patients With at Least one TEAE7762
Patients With at Least one TEAE Related to NKTR-2555752
Patients With at Least one Serious TEAE2251
Patients With at Least one Serious TEAE Related to NKTR-2550101
Patients With at Least one TEAE Leading to Death0000
Patients With at Least one TEAE Related to NKTR-255 Leading to Death0000
Patients With at Least one TEAE Leading to NKTR-255 Discontinuation0200
Patients With at Least one TEAE Leading to NKTR-255 Delay, Reduction, or Interruption2020
PrimaryThe 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
Reported as:
Number · µg/kg
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
µg/kgDose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose 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 EscalationNANANANA

Adverse events

Collected over Through study completion, up to 6 months.. Non-serious events are listed at a 5% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With Cetuximab2/8 (25%)2/7 (28.6%)7/7 (100%)
Dose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With Cetuximab4/8 (50%)2/7 (28.6%)7/7 (100%)
Dose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With Cetuximab1/6 (16.7%)5/6 (83.3%)6/6 (100%)
Dose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab1/3 (33.3%)1/3 (33.3%)2/3 (66.7%)
Most frequent serious events
Showing 10 of 13
Most frequent serious events
EventDose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab
Cytokine release syndromeImmune system disorders0/70/70/61/3
CellulitisInfections and infestations0/70/71/60/3
Lung infectionInfections and infestations0/70/71/60/3
SepsisInfections and infestations0/70/71/60/3
Urinary tract infectionInfections and infestations0/70/71/60/3
SyncopeNervous system disorders0/70/71/60/3
Urinary tract obstructionRenal and urinary disorders0/70/71/60/3
PneumoniaInfections and infestations0/70/71/60/3
Small intestinal obstructionGastrointestinal disorders1/70/70/60/3
AstheniaGeneral disorders1/70/70/60/3
Most frequent other events
Showing 10 of 87
Most frequent other events
EventDose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With Cetuximab
Infusion related reactionInjury, poisoning and procedural complications3/76/71/60/3
Dermatitis acneiformSkin and subcutaneous tissue disorders5/74/72/61/3
HypokalaemiaMetabolism and nutrition disorders1/70/73/60/3
Rash maculo-papularSkin and subcutaneous tissue disorders1/70/71/61/3
ChillsGeneral disorders1/71/72/61/3
Influenza like illnessGeneral disorders0/71/71/61/3
NauseaGastrointestinal disorders1/70/72/61/3
DiarrhoeaGastrointestinal disorders0/70/72/60/3
VomitingGastrointestinal disorders0/70/71/61/3
HypomagnesaemiaMetabolism and nutrition disorders1/70/72/60/3

Baseline characteristics

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
Age, Continuous(years)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
Mean60.7 ± 7.356.9 ± 11.4460.7 ± 18.0259.0 ± 11.0059.3 ± 11.75
Age, Customized
Age, Customized(participants)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
<65543214
>=65 and <7523218
>=75 and <8500101
>=8500000
Sex: Female, Male
Sex: Female, Male(Participants)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
Female02316
Male753217
Race/Ethnicity, Customized
Race/Ethnicity, Customized(Participants)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
Hispanic or Latino11204
Not Hispanic or Latino564318
Not Reported10001
Unknown00000
Race/Ethnicity, Customized
Race/Ethnicity, Customized(Participants)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
American Indian or Alaska Native00000
Asian00011
Black or African American11002
Native Hawaiian or Other Pacific Islander00000
White455115
Unknown10102
Not Reported11013
Eastern Cooperative Oncology Group (ECOG) Performance Status
Eastern Cooperative Oncology Group (ECOG) Performance Status(Participants)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
ECOG PS 0243110
ECOG PS 1533213
Height
Height(centimeter)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
Mean176.69 ± 6.370171.78 ± 7.202167.90 ± 14.675168.54 ± 3.062171.76 ± 9.635
Weight
Weight(kg)Dose Escalation of NKTR-255 Level 1 (1.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 2 (3.0 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 3 (4.5 µg/kg) With CetuximabDose Escalation of NKTR-255 Level 4 (6.0 µg/kg) With CetuximabTotal
Mean91.77 ± 14.41584.20 ± 14.35987.46 ± 44.88470.98 ± 17.72785.63 ± 25.341

1 further baseline measures are reported on the registry.

08

Study locations

6 sites
  • University of California, San Diego
    San Diego, California 92103, United States
  • University of California, San Francisco
    San Francisco, California 94158, United States
  • University of Minnesota
    Minneapolis, Minnesota 55455, United States
  • Mary Crowley Cancer Research
    Dallas, Texas 75230, United States
  • MD Anderson Cancer Center
    Houston, Texas 77030, United States
  • START Center for Cancer Care
    San Antonio, Texas 78229, United States
09

References and documents

Study documents

PDFs hosted by the registry, ClinicalTrials.gov.

10

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Jun 8, 2025, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
11

Registry details

Key details

Study ID
NCT04616196
Responsible party
Sponsor
First posted
Nov 4, 2020
Start date
Oct 30, 2020
Primary completion
Mar 30, 2023
Completion
Mar 30, 2023
Results posted
Jun 8, 2025
Last update
Jun 8, 2025

Study contacts

Study Director
study director · Nektar Therapeutics

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is completed, as verified in May 2025. You cannot join it, but the record below documents what was studied.

Follow this study

Get an email when the registry record changes — status, dates, results — or when someone posts here.

Sign in to follow

Discussion

Questions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.

Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.

Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.

Studies of the drug tested here: NKTR-255

Start the discussion