This clinical trial is for adults who have extensive stage small cell lung cancer (ES-SCLC) for which they have received no treatment.
   
The purpose of this study is to evaluate the effects of BNT327 (the “study drug”) when combined with chemotherapy (etoposide plus carboplatin), compared with standard of care, a drug called atezolizumab in combination with chemotherapy (etoposide plus carboplatin), to find out the following:
   
   --if the study drug can shrink your cancer or prevent your cancer from getting worse; 
   --if the study drug can help you live longer; 
   --if the study drug is safe, tolerable and effective against your type of cancer; 
   --how the study drug is processed by your body; 
   --how the study drug and your cancer affect how you are coping with your day-to-day life (called, “quality of life”). 
   
BNT327 is an investigational drug, which means it is not approved by the United States Food and Drug Administration (FDA). 
   
The drug atezolizumab in combination with chemotherapy (etoposide and carboplatin) has been approved in many countries worldwide for the first-line treatment of patients with ES-SCLC. However, these drugs are considered investigational in this study because they are not approved for use with BNT327.
   
The study has two stages. Currently, the study is in Stage 2. In Stage 2, participants are randomly (like tossing a coin) assigned to one of two dosing groups: The Control Group or the Treatment Group. The Control Group will receive atezolizumab in combination with chemotherapy (etoposide and carboplatin) and the Treatment group will receive BNT327 plus chemotherapy (etoposide and carboplatin). Participants will have a 50/50 (1 in 2) chance of being in one of two groups (BNT327 arm or control arm).
   
To obtain study data objectively, it is necessary that neither the participant nor the study doctor know whether the participant is receiving BNT327 or atezolizumab. This procedure is called “double-blinding.” If it is necessary for safety reasons, it can be determined immediately what the participant received in the study.
   
BNT327, atezolizumab, etoposide, and carboplatin are administered by IV (intravenous infusion, slowly through a plastic needle or small tube in a vein). Etoposide can sometimes be given orally (by mouth) in capsule form if approved by the study sponsor. The study doctor will tell participants if this is an option for them.
   
Participation in this research study will involve four 21-day cycles of combination therapy followed by 21-day cycles of BNT327 alone or atezolizumab alone until a participant’s disease worsens, the participant has severe side effects, the participant chooses to withdraw from the study, the study is stopped, or up to 2 years (whichever occurs first). There is also a period of follow-up after a participant’s last dose of study treatment.