Safety and efficacy of antibody-drug conjugates plus immunotherapy in solid tumours: A systematic review and meta-analysis

Background: Combining antibody-drug conjugate (ADCs) with immune checkpoint inhibitors (ICIs) is emerging as a promising treatment option to increase efficacy outcomes. However, concerns arise regarding the safety of these combinations, as some toxicities may overlap. Currently, there is still limited information about the safety profiles of this strategy.

Methods: A systematic review and meta-analysis was conducted to identify clinical trials investigating FDA-approved ADCs in combination with ICI drugs in the metastatic setting across all solid tumors. The primary endpoint of this study was the percentage of adverse events (AEs) of any grade and grade ≥ 3. Secondary endpoints include the percentage of patients with AEs leading to death, treatment discontinuation, proportion of complete responses (CR) and overall response rate (ORR). A parallel search was conducted to quantify the safety profile of ADCs and ICIs in monotherapy. Random effects models were used to estimate pooled outcomes.

Results: Sixteen trials involving 1,133 patients treated with ADC plus ICI met the inclusion criteria with six different ADCs evaluated. Overall, 55.3 % of patients developed grade ≥ 3 AEs, 30.0 % of patients had treatment discontinuation, and 3.0 % experienced AEs leading to death. When compared to trials evaluating ADC or ICI as monotherapy, the combination results in similar rates of the most common AEs. However, it increases the risk of specific toxicities, such as ILD/pneumonitis (15.0 % with T-DXd plus ICI vs. 11.5 % with T-DXd alone). The pooled ORR was 48.8 % (95 %CI 39.4 % - 58.4 %) and the CR rate was 9.0 % (95 %CI 5.5 - 14.5). PD-L1-positive tumors showed numerically better efficacy outcomes.

Conclusions: This meta-analysis shows that the safety profile of the ADC plus ICI is comparable to that of ADC monotherapy. However, it increases the risk of certain toxicities of special interest, such as ILD/pneumonitis, highlighting the need for careful monitoring.