Neuroendocrine Tumor Clinical Trial Monitor

Key Active Programs in Neuroendocrine Tumors (2026)

The NET Treatment Landscape in 2026

Neuroendocrine tumors (NETs) are a heterogeneous group of malignancies arising from neuroendocrine cells throughout the body — most commonly the gastrointestinal tract (midgut/hindgut), pancreas, and lung. Classification is based on differentiation (well vs. poorly differentiated) and proliferation grade (G1: Ki-67 <3%, G2: Ki-67 3–20%, G3: Ki-67 >20%), with well-differentiated grade 3 NETs representing a distinct biology from poorly differentiated neuroendocrine carcinomas (NECs, the SCLC-like entity).

The Four Lines of NET Therapy

• First line — Somatostatin analogs (SSA): Octreotide LAR (Sandostatin) or lanreotide (Somatuline) for SSR-positive NETs, based on PROMID and CLARINET trials
• Second line — mTOR or VEGFR inhibition: Everolimus (Afinitor, RADIANT-4 for non-pancreatic NETs; RADIANT-3 for pNETs) or sunitinib (Sutent, SUN1111 for pNETs)
• Third line — PRRT: Lutetium-177 DOTATATE (Lutathera) for SSR-positive GEP-NETs after SSA and everolimus failure — though the optimal sequencing is still debated
• Beyond PRRT: No established standard. Cabozantinib is used off-label; clinical trial enrollment is strongly recommended

Key Research Questions in NET Trials (2026)

Can zanzalintinib replace everolimus as second-line standard?

Everolimus has significant limitations as second-line NET therapy: response rates of only 5% (though disease stabilization is meaningful), class-effect metabolic toxicities (hyperglycemia, immunosuppression), and modest PFS improvement over placebo (11 months vs. 3.9 months in non-pNETs, RADIANT-4). Zanzalintinib targets VEGFR2, MET, AXL, and MERTK — a broader anti-angiogenic and anti-immune-suppressive profile than everolimus's mTOR inhibition. The Exelixis Phase 2/3 trial (NCT06943755) is the first prospective head-to-head comparison of a multi-kinase inhibitor versus everolimus in non-pancreatic NETs. If zanzalintinib shows superior PFS with manageable toxicity, it could displace everolimus in the second-line setting — a critical commercial opportunity for Exelixis.

What happens after Lutathera — can PRRT be retreated?

Lutetium-177 DOTATATE (Lutathera) is administered as 4 fixed cycles of 7.4 GBq every 8 weeks. After completing 4 cycles, a significant proportion of patients respond and maintain disease control, but eventually progress. The standard Lutathera protocol has no defined retreatment pathway. Two active NCI trials (NCT05773274 comparing retreatment vs. standard care; NCT04665739 exploring PRRT in broader populations) are generating data on retreatment feasibility, optimal timing, and cumulative renal/bone marrow dosimetry limits. These trials are critical for establishing evidence-based post-Lutathera pathways, which currently rely entirely on physician judgment and compassionate use.

DLL3 targeting: from SCLC to high-grade NETs

DLL3 is a Notch inhibitory ligand with very limited expression in normal adult tissues but high expression in neuroendocrine cancers — including SCLC (70–80%), large-cell neuroendocrine carcinoma (LCNEC), and high-grade extrapulmonary NETs. Tarlatamab's approval in SCLC (DeLLphi-301) opened the door to studying DLL3-targeting in the broader neuroendocrine carcinoma spectrum. The UCLA basket trial (NCT06788938) could expand tarlatamab's label if DLL3-positive high-grade NETs show response rates comparable to SCLC (~40% ORR in second-line). The key unknowns: DLL3 expression frequency in low-grade well-differentiated NETs (likely low) and whether the BiTE mechanism can overcome the immunosuppressive NET tumor microenvironment.

FAQ: Neuroendocrine Tumor Clinical Trials

What is the difference between a carcinoid tumor and a neuroendocrine tumor?

"Carcinoid" is an older term historically applied to well-differentiated NETs of the GI tract and lung. The WHO 2022 classification now prefers "neuroendocrine tumor" (NET) graded G1–G3, reserving "carcinoid" as an informal descriptor for clinical context. In modern clinical trials, "carcinoid" and "well-differentiated NET" are largely interchangeable for G1–G2 GI/lung NETs. High-grade tumors are called neuroendocrine carcinomas (NEC) — these behave like SCLC and are treated differently from well-differentiated NETs. Clinical trial eligibility typically specifies the Ki-67 grade and differentiation status to ensure the right patient population.

Do I need a DOTATATE scan to be eligible for PRRT trials?

Yes. All lutetium-177 DOTATATE trials require confirmed somatostatin receptor (SSR) positivity by DOTATATE PET scan (68Ga-DOTATATE or equivalent). The NETTER-1 eligibility required Krenning score ≥3 (higher uptake than liver). Most current trials use similar criteria. Patients with SSR-negative or low-expressing tumors (Krenning score 1–2) are typically excluded from PRRT trials. Pancreatic NETs can be SSR-positive or negative — those with SSR-negative pNETs are steered toward mTOR or VEGFR inhibitor trials rather than PRRT.

How do I know if my tumor is DLL3-positive and eligible for tarlatamab trials?

DLL3 positivity is assessed by immunohistochemistry (IHC) on tumor tissue. The SCLC trials used H-score or percentage positive as cutoffs — most trials require any DLL3 expression (>1% tumor cells positive). For the UCLA basket trial (NCT06788938), eligibility requires DLL3-expressing tumors by IHC as determined by local pathology. Well-differentiated G1–G2 NETs are unlikely to express DLL3 at high levels; poorly differentiated NECs and high-grade G3 NETs are more likely DLL3-positive. Patients interested in tarlatamab should ask their oncologist about DLL3 IHC testing on existing biopsy material.

What is the difference between DataLookout and a ClinicalTrials.gov search for "neuroendocrine"?

A ClinicalTrials.gov search for "neuroendocrine" returns 500+ studies including observational studies, biomarker collection studies, completed trials, and single-center Phase 1 dose-escalation studies. DataLookout's daily digest filters to Phase 2/3 industry and academic trials with active enrollment — the ones where NET patients can actually sign up. You can set alerts specifically for "neuroendocrine" Phase 2+ trials and receive notification when zanzalintinib opens new sites, when the tarlatamab basket trial updates enrollment criteria, or when a new PRRT intensification study launches.

Related Pages

• Pancreatic Cancer Clinical Trials (including pNETs)
• Small Cell Lung Cancer Clinical Trials
• Liver Cancer Clinical Trials (NET liver metastases)
• Rare Disease Clinical Trials