This Phase 1/2, multicenter, open-label, FIH study aims to evaluate the safety, tolerability, PK, and preliminary antitumor activity of CRN09682 in participants with SST2-expressing NENs and other solid tumors. The study includes a Dose Escalation Phase to determine the MTD and DLTs. Following MTD identification, additional participants will be enrolled at the expansion dose to further assess safety, tolerability, PK, and antitumor activity.

Inclusion Criteria:

• Have a histological diagnosis of metastatic or locally advanced inoperable NET, NEC, or other solid tumors that have confirmed radiological progression.
• Have one or more measurable disease location per RECIST version 1.1.
• Have a tumor that expresses SSR confirmed by SSR imaging.
• Have an ECOG performance status of 0, 1, or 2.

Exclusion Criteria:

• Have tumor progression while undergoing a course of PRRT or within 6 months of completing PRRT.
• Have brain metastases unless asymptomatic and stable for at least one month for participants with SCLC or LCLC or at least 3 months for participants with other non-NET solid tumors.
• Use of anticancer agents within specified intervals prior to the first dose of study drug.
• Had surgery, chemoembolization, or radiofrequency ablation within 90 days prior to first dose of study drug.
• Prior participation in any intervention clinical study within 30 days or 5 half-lives (whichever is longer) prior to the first dose of study drug.
• Participants with carcinoid syndrome.
• Secondary malignancy: participants who have any other malignancy known to be active or treated within 3 years of the start of screening, with the exception of treated cervical intraepithelial neoplasia, superficial (noninvasive) bladder cancer, and non-melanoma skin cancer.
• Have prior treatment with MMAE.
• Have hypersensitivity or history of anaphylactic reaction to octreotide, other SSAs, and/or MMAE.