Author: Anoma Ranaweera, Medical Writer, Auckland, New Zealand. DermNet Editor in Chief: Adjunct A/Prof Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. November 2018.

What is cemiplimab?

Cemiplimab (also called cemiplimab-rwlc; trade name Libtayo®) is a prescription medicine used to treat people with cutaneous squamous cell carcinoma (SCC).

In April 2018, the European Medicines Agency (EMA) accepted for review the Marketing Authorization Application for cemiplimab for the treatment of patients with metastatic cutaneous SCC or with locally advanced cutaneous SCC who were not candidates for surgery.

In September 2018, the US Food and Drug Administration (FDA) approved cemiplimab as a breakthrough therapy for the treatment of patients with metastatic cutaneous SCC or locally advanced SCC who are not candidates for curative surgery or curative radiation. Regeneron and Sanofi-Aventis (New Jersey, USA) will market Libtayo® jointly in the U.S.

Locally advanced cutaneous squamous cell carcinoma

Cemiplimab is the first and only treatment specifically approved and available for advanced cutaneous SCC in the U.S. This drug was evaluated by the FDA under Priority Review, which is reserved for medicines that represent significant improvements in safety or efficacy in treating serious conditions.

The EMA review process is anticipated to be complete in the first half of 2019. There are currently no EMA-approved treatments for advanced cutaneous SCC.

Cemiplimab is under investigation in other malignancies. It is in Phase III development for cervical cancer and basal cell carcinoma, and in Phase II development for other cancers including glioblastoma multiforme, ovarian and prostate cancers, and acute lymphocytic leukaemia.

Regulatory applications in additional countries are also being considered for submission later in 2018. Cemiplimab is currently not available in NZ.

How does cemiplimab work?

Cemiplimab is a human monoclonal antibody that targets the immune checkpoint receptor PD-1 (programmed cell death protein-1).

  • The programmed death receptor (PD-1) is a surface molecule expressed on antigen-stimulated T cells.
  • When unbound, the PD-1 receptor acts as an immune checkpoint receptor enabling self-tolerance by T cells, thus preventing autoimmune reactions.
  • However, the binding of PD-1 to its ligands, programmed death receptor ligand 1 (PD-L1) and programmed cell death ligand 2 (PD-L2), suppresses this immune response by inducing downstream signalling that inhibits the proliferation of T cells, cytokine release, and cytotoxicity.
  • Abnormal PD-L1 expression on the surface of squamous carcinoma cells activates PD-1 and suppresses cytotoxic T-cell activity.
  • This T-cell tolerance enables the tumour cells to avoid recognition and attack by the immune system.

Cemiplimab is a highly selective humanised monoclonal immunoglobulin G4 (IgG4) antibody that targets checkpoint inhibitor PD-1 and blocks its interaction with PD-L1 and PD-L2, releasing the PD-1 pathway-mediated inhibition of the immune response. This includes the antitumour immune response, thereby decreasing tumour growth.

How is cemiplimab administered?

The recommended dosage of cemiplimab is 350 mg as an intravenous infusion over 30 minutes every 3 weeks until disease progression decreases or an unacceptable toxicity is reached.

Dosage modification

Severe and fatal immune-mediated adverse reactions may necessitate withholding or discontinuing cemiplimab.

Cemiplimab should be withheld in the following conditions:

  • Grade 2 pneumonitis
  • Grades 2 or 3 colitis
  • Hepatitis (AST or ALT increased more than 3 and up to 10 times the upper limit of normal, or total bilirubin increased up to 3 times the upper limit of normal)
  • Grades 2, 3, or 4 endocrinopathies (withhold if clinically necessary)
  • Other immune-mediated Grade 3 adverse reactions involving a major organ.

Cemiplimab should be permanently discontinued in the following conditions:

  • Grades 3 or 4 pneumonitis
  • Grade 4 colitis
  • Hepatitis (AST or ALT increased more than 10 times the upper limit of normal or total bilirubin increased more than 3 times the upper limit of normal)
  • Grades 3 or 4 infusion-related reactions
  • Recurrent or persistent immune-mediated adverse reactions persistent for ≥ 12 weeks after the last dose or requiring prednisone ≥ 10 mg/day (or equivalent) for ≥12 weeks after last cemiplimab dose.

Renal impairment

No dosage adjustment is necessary for mild or moderate renal impairment, as no clinically important effect on the exposure of cemiplimab has been observed in population pharmacokinetic studies.

Hepatic impairment

No dosage adjustment is necessary for mild hepatic impairment, as no clinically important effect on the exposure of cemiplimab has been observed. There are no studies in patients with moderate or severe hepatic impairment.

What are potential drug interactions with cemiplimab?

No formal pharmacokinetic drug interaction studies have been conducted with cemiplimab.

What are the possible side effects of cemiplimab?

In clinical trials, the most common side effects (≥ 10%) in patients receiving cemiplimab up to 3 mg/kg every 2 weeks were:

  • Fatigue
  • Nausea
  • Pruritus (itch)
  • Rash (unspecified)
  • Decreased appetite
  • Constipation
  • Diarrhoea.

The most frequent (≥ 2%) serious adverse drug reactions observed with cemiplimab were urinary tract infection, sepsis, pneumonia, pneumonitis, and cellulitis. Cemiplimab can also cause infusion reactions including anaphylaxis.

Severe and fatal immune-mediated adverse effects

  • Cemiplimab binds to the programmed death receptor-1 (PD-1), blocking the PD-1/PD-L1 pathway, thereby removing inhibition of the immune response with the potential for breaking of peripheral tolerance and induction of immune-mediated adverse reactions.
  • Immune-mediated pneumonitis, colitis, hepatitis, endocrinopathies, hypophysitis (inflammation of the pituitary gland), hypothyroidism or hyperthyroidism, type 1 diabetes mellitus, and nephritis have been reported during clinical trials.
  • Other immune-mediated adverse reactions involving other systems (eg, neurological, cardiovascular, ocular reactions) were also reported in < 1% of patients in clinical trials.
  • Clinical chemistries, including liver tests and thyroid function tests, should be done at baseline and periodically during treatment and medical management instituted promptly.

Skin problems due to cemiplimab

Signs of these skin problems may include:

  • Rash
  • Itching
  • Blistering
  • Painful ulcers in the mouth, nose, throat and genital area.

What are the risks with cemiplimab?

Before receiving treatment with cemiplimab, the healthcare provider should be informed if the patient has any of the following.

  • Immune system problems such as Crohn disease, ulcerative colitis, or systemic lupus erythematosus
  • A history of organ transplantation
  • Lung or breathing problems
  • Liver or kidney problems
  • A history of diabetes
  • Pregnant or plan to become pregnant
  • Breastfeeding or plans to breastfeed

The use of cemiplimab in specific populations

Pregnant women

  • Based on its mechanism of action, cemiplimab can cause fetal harm when administered to a pregnant woman.
  • Human IgG4 immunoglobulins are known to cross the placenta; therefore cemiplimab has the potential to be transmitted from the mother to the developing fetus.
  • Animal studies have demonstrated that inhibition of the PD1/PD-L1 pathway can lead to increased risk of immune-mediated rejection of the developing fetus resulting in fetal death.
  • There is no available data on the use of cemiplimab in pregnant women.

Nursing mothers

It is not known whether cemiplimab or its metabolites are excreted in human milk. Because many drugs are excreted in human milk, mothers should discontinue nursing prior to using cemiplimab.

Females of reproductive potential

Females of reproductive potential should be advised to use effective contraception during treatment with cemiplimab and for at least 4 months after the last dose.


The safety and effectiveness of cemiplimab have not been established in children.

Older people

In clinical studies, of the 163 patients with metastatic and locally advanced cutaneous SCC who received cemiplimab, 72% were 65 years or older and 37% were 75 years or older. No overall differences in safety or effectiveness were observed between these and younger patients.

New Zealand approved datasheets are the official source of information for these prescription medicines, including approved uses and risk information. Check the individual New Zealand datasheet on the Medsafe website.


Related information



  • Papadopoulos KP, Owonikoko TK, Johnson ML, et al. REGN2810: A fully human anti-PD-1 monoclonal antibody, for patients with unresectable locally advanced or metastatic cutaneous squamous cell carcinoma (CSCC) — Initial safety and efficacy from expansion cohorts (ECs) of phase I study. J Clin Oncol. 2017; 35: 9503. Journal
  • Rischin CD, Migden MR, Chang A, et al. Primary analysis of phase 2 results for cemiplimab, a human monoclonal anti-PD-1, in patients with metastatic cutaneous squamous cell carcinoma (mCSCC). J Clin Oncol. 2018; 36: 9519. Journal
  • Migden MR, Rischin CD, Schmults A, et al. PD-1 blockade with cemiplimab in advanced cutaneous squamous-cell carcinoma. N Engl J Med. 2018; 379: 341–51. doi: 10.1056/NEJMoa1805131. PubMed

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