Peptide-Drug Conjugates for Cancer: How Peptides Are Changing Oncology

The idea of using peptides to target cancer cells dates to the early 2000s, when researchers identified that certain receptors are overexpressed on tumor surfaces. The somatostatin receptor, for example, appears at high density on neuroendocrine tumors but at low density on healthy tissue. If you could attach a radioactive particle or a toxic drug to a peptide that binds somatostatin receptors, you could deliver the payload specifically to cancer cells. The first major success was Lutathera (lutetium 177 dotatate), approved in 2018 for gastroenteropancreatic neuroendocrine tumors. It uses a somatostatin analog peptide to carry a radioactive isotope to tumor cells. Then came Pluvicto, which targets prostate-specific membrane antigen (PSMA) on prostate cancer cells. Pluvicto received initial FDA approval in 2022 for metastatic castration-resistant prostate cancer after chemotherapy. The March 2026 expansion moved it to earlier treatment lines, before chemotherapy, based on positive Phase 3 results. The PDC field has accelerated since then. As of 2026, over 80 new peptide-drug conjugates have entered clinical trials since 2022, with many using AI-optimized peptide sequences to improve targeting precision.

A PDC has three components: a targeting peptide, a linker, and a cytotoxic payload. The targeting peptide binds to a receptor that is overexpressed on cancer cells but scarce on healthy cells. Once bound, the cancer cell internalizes the conjugate through receptor-mediated endocytosis. Inside the cell, the linker breaks down (often in the acidic environment of a lysosome), releasing the cytotoxic drug. The drug then kills the cancer cell from within. The advantage over antibody-drug conjugates is size. Antibodies are large molecules (about 150 kDa) that have difficulty penetrating solid tumors. Peptides are much smaller (typically 1 to 5 kDa), so they diffuse into tumor tissue more readily. They also clear from the bloodstream faster, which can reduce systemic toxicity. Manufacturing is simpler and cheaper because peptides can be synthesized chemically rather than produced in cell culture. The tradeoff is that peptides can be degraded by proteases in the blood, so the linker chemistry must be carefully engineered to protect the peptide until it reaches the target.

The clinical results depend on the specific PDC, but Pluvicto provides the clearest example: Pluvicto (177Lu-PSMA-617): In the Phase 3 VISION trial, Pluvicto plus standard of care improved overall survival by 4 months compared to standard of care alone in metastatic prostate cancer. The 2026 expansion was based on the PSMAfore trial, which showed that Pluvicto delayed disease progression significantly when used before chemotherapy. Radiographic progression-free survival was roughly doubled compared to the change of ARPI (androgen receptor pathway inhibitor) arm. Other PDCs in development:

• ANG1005 (paclitaxel conjugated to angiopep-2): Targets brain tumors by crossing the blood-brain barrier. Phase 3 data expected 2026.
• CBP-1018 (targeting folate receptor): In trials for ovarian and other solid tumors.
• Multiple theranostic PDCs that combine diagnostic imaging and therapy in one molecule.

PDC treatment is fundamentally different from traditional chemotherapy. Because the cytotoxic drug is delivered directly to cancer cells, systemic side effects are typically milder. A user on r/prostatecancer described their Pluvicto experience: “Six cycles so far. The worst part is the dry mouth, which they call xerostomia. It started after the second infusion and has been persistent. Fatigue hits about a week after each cycle and lasts a few days. Blood counts drop a bit but have recovered between cycles. Way easier than docetaxel was.“ Another patient noted: “The radiation safety precautions are annoying. For about a week after each infusion, I need to limit close contact with family. Flush the toilet twice, that kind of thing. But the scans show the tumors shrinking, so it is worth it.“ Common side effects across PDCs include fatigue, nausea (usually mild), injection site reactions, and target-specific effects. For Pluvicto, xerostomia (dry mouth from salivary gland uptake of the radioligand) is the most distinctive side effect. For non-radioactive PDCs, the toxicity profile depends on the payload drug.

• More targeted treatment with fewer systemic side effects than traditional chemotherapy
• Tumor shrinkage or stabilization visible on imaging (CT, PET, or MRI)
• Improved tumor markers (PSA for prostate cancer, chromogranin A for neuroendocrine tumors)
• Better quality of life during treatment compared to conventional chemotherapy
• Ability to combine with other therapies (immunotherapy, targeted therapy) due to non-overlapping toxicity
• Potential for theranostic pairing: the same peptide can carry a diagnostic isotope for imaging and a therapeutic isotope for treatment

This section differs from other peptide guides because PDCs are pharmaceutical treatments, not wellness peptides. The “pairing“ here refers to complementary approaches during PDC cancer therapy.

• BPC-157: Has shown mucosal protective effects that may help manage GI side effects from PDC treatment. Preclinical data suggests it supports tissue repair and reduces inflammation. Patients sometimes use it for gut health during cancer treatment, though this is off-label.
• GHK-Cu: Supports wound healing and tissue repair. May help with skin and mucosal recovery during cancer treatment. Some integrative oncology practitioners recommend copper peptides for skin health during radiation-adjacent therapies.
• Thymosin alpha-1: Has been studied in combination with cancer immunotherapy. It enhances T-cell function and may complement the immune-mediated anti-tumor effects of some PDCs. Several clinical trials are evaluating thymosin alpha-1 combined with checkpoint inhibitors.
• Kisspeptin: Being studied for its role in hormone-sensitive cancers. In prostate cancer, kisspeptin-based approaches could theoretically complement PDCs that target hormone-driven tumors.