Small Cell Lung Cancer (SCLC) Clinical Trials

• Histologically confirmed small cell lung cancer diagnosis

• Diagnosis made with excisional or core needle biopsy specimen (fine needle aspirate may be permitted with approval from the Medical Monitor)

• Subjects must submit tumor sample per the laboratory manual, defined as follows: 1L Cohort - Tissue obtained prior to the initiation of 1L therapy; 2L Cohort - Tissue obtained prior to the initiation of 1L therapy and/or a standard of care re-biopsy prior to the start of 2L therapy, if performed.

• ECOG performance status of 0-2 at time of enrollment

• For participants entering prior to first line therapy, planned extensive stage first-line therapy of etoposide plus platinum plus PD-L1 inhibitor (atezolizumab or durvalumab)

• For participants entering post completion of standard of care first line prior to second line therapy, completion of an EP+CPI with or without maintenance therapy. Note: Participants who received 1L therapy that is not standard of care i.e., investigational therapy, are not eligible.

• Extensive stage disease at time of diagnosis according to NCCN definition: Extensive Stage Small Cell Lung Cancer (SCLC) as either Stage IV disease (any T, any N, with M1a/b/c) or T3-4 disease due to multiple lung nodules that are too extensive or have a tumor/nodal volume that is too large to be encompassed in a tolerable radiation plan (NCCN version 2.2026-September 16, 2025).

• Willing and able to provide informed consent

• Palliative radiotherapy is permitted as long as there is measurable disease outside of the radiotherapy port with which to assess response to therapy delivered

∙ Participants will be excluded from the study if any of the following criteria apply. The participant has/is:

• Patients with a secondary malignancy must have been both diagnosed \> 3 years from the lung cancer of interest and have completed all therapy for that malignancy \> 3 years prior to diagnosis of the lung cancer of interest, with the exception of the following:

‣ Patients with superficial basal cell carcinoma of low-risk histology per NCCN Guidelines (Low-risk histologic subtypes include nodular, superficial, and other non-aggressive growth patterns such as keratotic, infundibulocystic, and fibroepithelioma of Pinkus) and low-risk for recurrence per NCCN Guidelines (location on trunk or extremities, size \< 2 cm, primary (not recurrent), with well-defined borders) can be included even if they are diagnosed \< 3 years from the lung cancer of interest.

⁃ Patients with superficial squamous cell carcinoma of low-risk pathology per NCCN Guidelines (verrucous, keratoacanthomatous) and low-risk for recurrence per NCCN Guidelines (located on trunk or extremities; ≤ 2 cm in size; primary lesion (vs. recurrent); well to moderately differentiated; \< 2 mm thick and no invasion beyond subcutaneous fat; negative for perineural invasion; and negative for lymphatic or vascular involvement) can be included even if they are diagnosed \< 3 years from the lung cancer of interest.

• Mixed small cell and non-small cell histology

• Small cell cancers of origin in other organs or suspected metastatic cancer from other sites (i.e., those without a known or suspected lung primary diagnosis)

• Large Cell Neuroendocrine cancers

• Carcinoids or atypical carcinoid tumors

• Transformed small cell lung cancer emerging in the setting of targeted therapy for NSCLC

• Treated with an investigational agent of another immunotherapy class (i.e., non PD-1 or PD-L1 inhibitor)

• Not willing to have additional blood samples collected