Analogs of peptide hormones (LH-RH, somatostatin, bombesin) can be chemically linked to cancer drugs to deliver targeted chemotherapy to tumors, with one compound reaching phase II clinical trials.
Phase II clinical trialsAN-152, a doxorubicin-conjugated LH-RH analog, showed disease stabilization and objective responses in ovarian/endometrial cancer patients and advanced to phase II testing
What the researchers found
Peptide hormones can be chemically attached to cancer-killing drugs (cytotoxic agents) to create targeted chemotherapy that homes in on tumors expressing specific peptide receptors. The review covers three families of peptide-drug conjugates: LH-RH analogs (AN-152, AN-207) carrying doxorubicin that target LH-RH receptors on prostate, breast, ovarian, and endometrial cancers; somatostatin analogs (AN-162, AN-238) targeting somatostatin receptors on prostate, mammary, pancreatic, colorectal, gastric, and brain cancers; and bombesin/GRP analogs (AN-215) targeting bombesin receptors.
All three approaches suppressed tumor growth and metastases in preclinical models. The LH-RH conjugate AN-152 reached clinical trials: in phase I testing in women with ovarian or endometrial cancer, it showed disease stabilization and objective tumor responses. Phase II trials were underway at the time of publication, with additional trials pending in prostate, pancreatic, and bladder cancers.
Why it matters
This review by Nobel laureate Andrew Schally represents a pioneering approach to cancer therapy — using the body's own peptide receptor systems as homing beacons to deliver chemotherapy directly to tumors. Unlike antibody-drug conjugates (ADCs), peptide-drug conjugates (PDCs) are smaller, cheaper to produce, and can penetrate tumors more effectively. The concept laid groundwork for what has become an expanding field in targeted cancer therapy.
The numbers in context
3 peptide conjugate families · AN-152 (LH-RH-DOX) in phase I/II trials · Disease stabilization + objective responses in ovarian/endometrial cancer · Targets: LH-RH, somatostatin, bombesin/GRP receptors · 10+ cancer types targeted
How the study worked
Comprehensive review by the Schally group summarizing their work on cytotoxic peptide analogs for targeted cancer therapy. Covers preclinical development (in vitro and animal models) and early clinical trial results for LH-RH analog AN-152 in women with gynecological cancers. Published in Current Drug Delivery.
Who was studied
Cancer patients (gynecological cancers in clinical trials; multiple cancer types in preclinical models)
What this study cannot tell us
Review focuses primarily on the Schally group's own work, which may present a selective view. Phase I/II clinical data showed promise but the abstract doesn't report detailed efficacy numbers or long-term outcomes. Many of the compounds discussed were still in early clinical development at the time of publication (2011). The broader challenge of peptide-drug conjugate stability and pharmacokinetics is acknowledged but not fully resolved.
How to read the evidence
This is an authoritative review by a Nobel Prize-winning researcher in the field. It combines extensive preclinical data with early clinical trial results. However, the clinical evidence was still in early phases at the time of publication, and the review primarily represents the authors' own research program.
When this study was published
Published in 2011. This is a foundational review for the peptide-drug conjugate field. While the specific compounds discussed have been further developed or superseded, the concept of peptide-targeted chemotherapy has grown into an active area of cancer drug development.
The bigger picture
Peptide-drug conjugates (PDCs) represent a parallel track to antibody-drug conjugates (ADCs), which have become blockbuster cancer drugs. PDCs have potential advantages: smaller size for better tumor penetration, lower production costs, and the ability to target peptide receptors that antibodies can't easily reach. The Schally group's work helped establish this entire field, and modern PDC research continues to build on these foundations with improved linker chemistry and more potent payloads.
Questions still open
- How did AN-152 perform in the phase II trials that were underway at the time of this review?
- Can modern linker chemistry and payload technology improve on the first-generation peptide-drug conjugates described here?
- Will peptide-drug conjugates eventually compete with antibody-drug conjugates for mainstream cancer treatment?
Common questions
What are peptide-drug conjugates and how do they fight cancer?
Who is Andrew Schally and why is this research significant?
Read the original research
Use of analogs of peptide hormones conjugated to cytotoxic radicals for chemotherapy targeted to receptors on tumors.
Current drug delivery, 8(1), 11-25
Citation
Schally, Andrew V; Engel, Jorg B; Emons, Gunter; Block, Norman L; Pinski, Jacek. (2011). Use of analogs of peptide hormones conjugated to cytotoxic radicals for chemotherapy targeted to receptors on tumors.. Current drug delivery, 8(1), 11-25.