Toxic Epidermal Necrolysis Induced by Sintilimab: A Case Report

Immune checkpoint inhibitors are anticancer drugs with clear curative effects. Programmed cell death protein 1 (PD1), an immune checkpoint expressed in T, B, and NK cells, normally induces self-tolerance. Tumor cells overexpress programmed death ligand-1/2 (PD-L1/PD-L2) and bind to lymphocytic PD-1 to suppress T cell inflammatory activity, thereby achieving tumor escape. Sintilimab is a fully humanized IgG4 monoclonal antibody that specifically binds to PD-1 and blocks its interaction with PD-L1/PD-L2, lifting T cell suppression and therefore blocking the escape pathway of tumor cells1. Since the inhibitors activate T cells detrimental to self-tolerance, immune-related adverse events (irAEs) can occur. PD1 blockers related irAEs, including toxic epidermal necrolysis (TEN)2, 3, are reported for nivolumab and pembrolizumab3, 4, but not for sintilizumab. This article assesses a sintilimab-induced TEN, hoping to provide a reference for the drug’s safety.

A 72 year-old male patient was admitted on August 5, 2019 with lung cancer suspicion. Imaging assessment showed left lower lobe mass, consistent with lung cancer, multiple hepatic, cerebral, left adrenal metastases. Lung puncture pathology showed non-small cell lung cancer (NSCLC). Poorly differentiated carcinoma with non-specific immunohistochemical expression is usually poorly differentiated squamous cell carcinoma. Genetic testing showed no EGFR/ALK/ROS1/BRAF/MET/RET mutations. Body surface area (BSA) being 1.91 m², the patient received: sintilimab 200 mg, ivgtt, qd on August 28; paclitaxel 270 mg, ivgtt, qd on the 29th; carboplatin 0.6 g, ivgtt, qd on the 30th. The patient was discharged on August 31.

On September 21, the patient was readmitted with an extensive rash and diffuse itching which had appeared for 7 days (Fig. 1). Physical examination: T=36.6℃; macules, blisters, bullae and erosions located on the face, trunk, and limbs (Fig. 1); red erosions, blood scabs and pale yellow exudate situated periocularly, on the lip mucosa, genitally and perianally. Score of toxic epidermal necrolysis=3 points. The diagnosis of TEN was made, considered a Sintilizumab-induced irAEs.

Fig. 1
Posterior (A) and anterior (B) image of the patient. Large, confluent dusky red macules, flaccid blisters, bullae and erosions localized on the trunk and proximal portions of the limbs, affecting >30% of the body surface area. We received the patient’s consent form about publishing all photographic materials.

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Following pharmacologic treatment (Table 1) and wound care, the patient gradually improved. On October 16th, most crusts fell off, the original erosions were completely healed and the patient was discharged.

Table 1
Pharmacologic treatment of toxic epidermal necrolysis

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Dermatologic irAEs include pruritus, dermatitis, maculopapular rash, Sweet syndrome and TEN. In a third-level toxic reaction, the treatment could be rechallenged, while a fourth-level one require permanent treatment discontinuation5. According to the Common Terminology Criteria for Adverse Events of National Cancer Institute, TEN is classified as the level 4 for its characteristic that patients have skin sloughing off covering ≥30% BSA with associated symptoms (e.g., erythema, purpura, or epidermal detachment)6.

In TEN, identifying the disease-causing drugs is crucial. Causal evaluation was performed based on the algorithm of drug causality for epidermal necrolysis (ALAND)7, sintilimab=4 points, “probably”; paclitaxel and carboplatin=0 points, “unlikely”. The detailed calculating procedures of ALAND was referred to Sassolas et al.7 In this case, the delay from initial drug component intake to onset of reaction (index day) is 24, 23, and 22 days for the sintilimab, paclitaxel and carboplatin respectively. The elimination half-life of the sintilimab, paclitaxel and carboplatin is 13.7 days, 52.7 hours, and 3.5 hours, respectively. Besides, irAEs have been reported in the clinical use of sintilimab, but not in the paclitaxel and carboplatin. Qualitative analysis was performed according to the national Food and Drug Administration: manifestations began 24 days after using sintilimab; TEN belongs to the irAEs known in the drug’s instructions; TEN improved after drug withdrawal; sintilimab was discontinued; the effects of combined medication and disease progression can not be ruled out. Based on the aforementioned judgments, sintilimab is the most likely to have caused TEN.

Keratinocytes apoptosis is mainly mediated by CD8+ cytotoxic T and NK cells8. In a nivolumab-induced TEN, the number of CD8+ lymphocytes in the dermal-epidermal junction and the keratinocyte PD-L1 expression increased from the initial biopsy to the appearance of TEN2. The mechanisms in both cases may be similar.

In NSCLC patients with negative EGFR/ALK/ROS1/BRAF tests, guidelines9 recommend PD-1/PD-L1 antibody therapy alone or in combination with chemotherapy. The clinical trial ORIENT-12 confirmed safety of sintilimab with pemetrexed/platinum for advanced NSCLC. Moreover, sintilimab is currently the only PD-1 monoclonal antibody listed in the national medical insurance catalog. In conclusion, if immune checkpoint inhibitors need to be extrapolated clinically, strictly following evidence-based research, promptly detecting and treating adverse reactions is crucial.