A Novel Class of On-Treatment Cancer Immunotherapy Biomarker: Trough Levels of Antibody Therapeutics in Peripheral Blood

Pretreatment albumin is a prognostic and predictive biomarker for response to atezolizumab across solid tumors

Objectives

Reliable predictive biomarkers for response to immune checkpoint inhibition (ICI) are lacking. Pretreatment serum albumin, a known prognostic and predictive factor in ICI-treated patients, has been proposed as a potential pharmacokinetic surrogate marker for anti-PD1/PD-L1 antibodies, as it shares a homeostatic pathway with IgG. However, this hypothesis is currently based on theoretical considerations and limited evidence from retrospective data. Therefore, we comprehensively investigated the prognostic and predictive value of pretreatment albumin and its relationship with anti-PD-L1 IgG levels.

Methods

We analysed pretreatment albumin and atezolizumab serum levels and clinical response in four trials (IMvigor210, IMvigor211, IMmotion151 and OAK) of patients with metastatic lung-, renal- or urothelial cancer who received atezolizumab alone or in combination.

Results

A total of 3391 patients were analysed. Correlation between serum albumin and atezolizumab levels was weak (Pearson's coefficient 0.23). We found a strong prognostic value for pretreatment serum albumin across all trials. Both atezolizumab serum levels and serum albumin were independently correlated with overall survival. Importantly, in the three randomised phase III clinical trials, the survival benefit for immunotherapy compared with the active comparator arm was limited to patients with pretreatment serum albumin > 35 g L-1.

Conclusion

Our data do not support the hypothesis that albumin serves as a surrogate for atezolizumab pharmacokinetics. However, we show that albumin on its own exerts strong prognostic value for patients treated with immunotherapy. As benefit from immunotherapy was limited to patients with normal/elevated serum albumin levels, baseline albumin could potentially be used as a predictive marker for immune checkpoint inhibition.

Cancer Immunology and Immunotherapy: From Defining Basic Immunology to Leading the Fight Against Cancer

The past decade has seen the advent and widespread use of several immunotherapeutic modalities that have markedly improved treatment outcomes for patients with various cancers. Nevertheless, the study of cancer immunology traces its roots back to the inception of modern immunology, and played a critical role in the of discovery of central immunological concepts and development of key technologies and methodologies and that have propelled advances in all areas of immunology.