Multi-Targeted Tyrosine Kinase Inhibitor-Induced Hyperammonemic Encephalopathy: a Report of Two Cases Using Pazopanib, Sunitinib, and Regorafenib

Hyperammonemic encephalopathy after tyrosine kinase inhibitors: A literature review and a case example

OBJECTIVE

To review the evidence of uncommon but fatal adverse event of hyperammonemic encephalopathy by tyrosine kinase inhibitors (TKI) and the possible mechanisms underlying this condition and to describe the case of a patient that developed drug-induced hyperammonemic encephalopathy related to TKI.

DATA SOURCES

Literature search of different databases was performed for studies published from 1 January 1992 to 7 May 2023. The search terms utilized were hyperammonemic encephalopathy, TKI, apatinib, pazopanib, sunitinib, imatinib, sorafenib, regorafenib, trametinib, urea cycle regulation, sorafenib, carbamoyl-phosphate synthetase 1, ornithine transcarbamylase, argininosuccinate synthetase, argininosuccinate lyase, arginase 1, Mitogen activated protein kinases (MAPK) pathway and mTOR pathway, were used individually search or combined.

DATA SUMMARY

Thirty-seven articles were included. The articles primarily focused in hyperammonemic encephalopathy case reports, management of hyperammonemic encephalopathy, urea cycle regulation, autophagy, mTOR and MAPK pathways, and TKI.

CONCLUSION

Eighteen cases of hyperammonemic encephalopathy were reported in the literature from various multitargeted TKI. The mechanism of this event is not well-understood but some authors have hypothesized vascular causes since some of TKI are antiangiogenic, however our literature review shows a possible relationship between the urea cycle and the molecular inhibition exerted by TKI. More preclinical evidence is required to unveil the biochemical mechanisms responsible involved in this process and clinical studies are necessary to shed light on the prevalence, risk factors, management and prevention of this adverse event. It is important to monitor neurological symptoms and to measure ammonia levels when manifestations are detected.

Sunitinib-induced hyperammonemic encephalopathy in metastatic gastrointestinal stromal tumors: A case report

BACKGROUND

Sunitinib, a multi-targeted tyrosine kinase inhibitor (TKI), has been approved for the salvage treatment of gastrointestinal stromal tumors (GIST). Hyperammonemic encephalopathy is a rare but severe complication of sunitinib use. Here, we present the case of a 66-year-old male with metastatic GIST without underlying liver cirrhosis who developed sunitinib-induced hyperammonemic encephalopathy.

CASE SUMMARY

A 66-year-old male with metastatic GIST was admitted because of reduced consciousness. Imatinib was administered as the first-line systemic therapy. He experienced repeated episodes of peritonitis due to tumor perforation, and surgery was performed. Progressive disease was confirmed based on increased liver metastasis, and sunitinib was initiated as a salvage treatment. However, 23 d after the third course of sunitinib, he presented to the emergency room with an episode of altered consciousness and behavioral changes. Based on the patient clinical history and examination findings, sunitinib-induced encephalopathy was suspected. Sunitinib was discontinued, and the patient was treated for hyperammonemia. The patient had a normal level of consciousness four days later, and the serum ammonia level gradually decreased. No further neurological symptoms were reported in subsequent follow-ups.

CONCLUSION

TKI-induced hyperammonemic encephalopathy is potentially life-threatening. Patients receiving TKIs experiencing adverse reactions should undergo systemic evaluation and prompt treatment.

A Case of Non-cirrhotic Hyperammonemic Encephalopathy in a Patient With Metastatic Gastrointestinal Stromal Tumor

Acute toxic encephalopathy (ATE) is a widely recognized medical emergency with an expansive differential. One particular known etiology for ATE is elevated ammonia, a powerful neurotoxin that often presents with clinical findings of confusion, disorientation, tremors, and in severe cases, coma and death. Hyperammonemia is most commonly associated with liver disease and presents as hepatic encephalopathy in the setting of decompensated cirrhosis; however, in rare cases, a patient may suffer from non-cirrhotic hyperammonemic encephalopathy. We describe the case of a 61-year-old male with metastatic gastrointestinal stromal tumor who was diagnosed with non-cirrhotic hyperammonemic encephalopathy, and briefly explore the literature describing its mechanisms.

Sunitinib-associated hyperammonemic encephalopathy

Sunitinib-associated hyperammonemic encephalopathy has not been previously reported in the emergency medicine literature. As newer treatments for cancer become more widespread and patients live longer, the emergence of previously unreported or rare adverse effects is expected to increase. Here we report the case of a 71-year-old woman with infiltrating ductal carcinoma of the breast with metastasis to the liver who developed hyperammonemic encephalopathy after taking sunitinib for 12 days. She presented to the emergency department (ED) with confusion and the initial workup revealed an elevated ammonia level (202 μmol/L; reference range, 11-51 μmol/L) without evidence of cirrhosis or portal hypertension. The patient was started on lactulose and admitted to the hospital, where her ammonia levels and mental status waxed and waned throughout her 12-day hospitalization. Further workup with magnetic resonance imaging and an electroencephalogram were negative. After 12 days, her ammonia level normalized and she was discharged without re-initiating Sunitinib. The patient was followed for three months post hospitalization without recurrence of symptoms. Patients on sunitinib should have their ammonia levels checked when presenting to the ED with altered mentation for early identification of hyperammonemic encephalopathy and its potential complications, such as seizures, brain edema, and death. Emergent management in the ED should include initiation of lactulose and consultation with the gastroenterology team.