Lymphodepletion - an essential but undervalued part of the chimeric antigen receptor T-cell therapy cycle

Lymphodepletion (LD) or conditioning is an essential step in the application of currently used autologous and allogeneic chimeric antigen receptor T-cell (CAR-T) therapies as it maximizes engraftment, efficacy and long-term survival of CAR-T. Its main modes of action are the depletion and modulation of endogenous lymphocytes, conditioning of the microenvironment for improved CAR-T expansion and persistence, and reduction of tumor load. However, most LD regimens provide a broad and fairly unspecific suppression of T-cells as well as other hematopoietic cells, which can also lead to severe side effects, particularly infections. We reviewed 1271 published studies (2011-2023) with regard to current LD strategies for approved anti-CD19 CAR-T products for large B cell lymphoma (LBCL). Fludarabine (Flu) and cyclophosphamide (Cy) (alone or in combination) were the most commonly used agents. A large number of different schemes and combinations have been reported. In the respective schemes, doses of Flu and Cy (range 75-120mg/m2 and 750-1.500mg/m2) and wash out times (range 2-5 days) differed substantially. Furthermore, combinations with other agents such as bendamustine (benda), busulfan or alemtuzumab (for allogeneic CAR-T) were described. This diversity creates a challenge but also an opportunity to investigate the impact of LD on cellular kinetics and clinical outcomes of CAR-T. Only 21 studies explicitly investigated in more detail the influence of LD on safety and efficacy. As Flu and Cy can potentially impact both the in vivo activity and toxicity of CAR-T, a more detailed analysis of LD outcomes will be needed before we are able to fully assess its impact on different T-cell subsets within the CAR-T product. The T2EVOLVE consortium propagates a strategic investigation of LD protocols for the development of optimized conditioning regimens.

Evaluation of Five Commercial SARS-CoV-2 Antigen Tests in a Clinical Setting

BACKGROUND

Point-of-care antigen tests (AgTs) for the detection of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) enable the rapid testing of infected individuals and are easy-to-use. However, there are few studies evaluating their clinical use.

OBJECTIVE

The present study aimed to evaluate and compare the clinical performance characteristics of various commercial SARS-CoV-2 AgTs.

DESIGN

The sensitivity of five AgTs, comprising four rapid antigen tests (RAT; AMP Rapid Test SARS-CoV-2 Ag, NADAL COVID-19 Antigen Rapid Test, CLINITEST Rapid COVID-19 Antigen Test, and Roche SARS-CoV-2 Rapid Antigen Test) and one sandwich chemiluminescence immunoassay (CLIA; LIAISON SARS-CoV-2 Assay), were evaluated in 300 nasopharyngeal (NP) swabs. Reverse transcriptase (RT) polymerase chain reaction (PCR) was used as a reference method.

PARTICIPANTS

NP swabs were collected from patients admitted to hospital due to COVID-19.

KEY RESULTS

Sensitivities of the AgTs ranged from 64.9 to 91.7% for samples with RT-PCR cycle threshold (Ct) values lower than 30 and were 100% for cycle threshold (Ct) values lower than 20. The highest sensitivity was observed for CLINITEST Rapid COVID-19 Antigen Test, and Roche SARS-CoV-2 rapid antigen test. Multivariate analysis using time from symptom onset and the Ct value for AgT sensitivity showed an inverse correlation. Further, the female sex was an independent factor of lower RAT sensitivity.

CONCLUSIONS

Antigen tests from NP swab samples show high sensitivity in patients with a Ct value < 20. The best clinical sensitivity can be obtained using AgTs within the first 6 days after symptom onset.

A Model Predicting Mortality of Hospitalized Covid-19 Patients Four Days After Admission: Development, Internal and Temporal-External Validation

Objective

To develop and validate a prognostic model for in-hospital mortality after four days based on age, fever at admission and five haematological parameters routinely measured in hospitalized Covid-19 patients during the first four days after admission.

Methods

Haematological parameters measured during the first 4 days after admission were subjected to a linear mixed model to obtain patient-specific intercepts and slopes for each parameter. A prediction model was built using logistic regression with variable selection and shrinkage factor estimation supported by bootstrapping. Model development was based on 481 survivors and 97 non-survivors, hospitalized before the occurrence of mutations. Internal validation was done by 10-fold cross-validation. The model was temporally-externally validated in 299 survivors and 42 non-survivors hospitalized when the Alpha variant (B.1.1.7) was prevalent.

Results

The final model included age, fever on admission as well as the slope or intercept of lactate dehydrogenase, platelet count, C-reactive protein, and creatinine. Tenfold cross validation resulted in a mean area under the receiver operating characteristic curve (AUROC) of 0.92, a mean calibration slope of 1.0023 and a Brier score of 0.076. At temporal-external validation, application of the previously developed model showed an AUROC of 0.88, a calibration slope of 0.95 and a Brier score of 0.073. Regarding the relative importance of the variables, the (apparent) variation in mortality explained by the six variables deduced from the haematological parameters measured during the first four days is higher (explained variation 0.295) than that of age (0.210).

Conclusions

The presented model requires only variables routinely acquired in hospitals, which allows immediate and wide-spread use as a decision support for earlier discharge of low-risk patients to reduce the burden on the health care system.

Clinical Trial Registration

Austrian Coronavirus Adaptive Clinical Trial (ACOVACT); ClinicalTrials.gov, identifier NCT04351724.