The ocean as a blue pharmacy: how promising are marine peptides?

Peptides are chains of amino acids, the building blocks of life, and are used in medicines, supplements and cosmetics. Pharmaceutical companies and research groups are constantly searching for new peptides and for inspiration to design them in the lab. In that search, they set their sights on the ocean. After all, its vast biodiversity makes it a rich source of organic molecules with a wide range of properties, some of which could have benefits for human health. Inevitably, environmental questions also come to the surface. Is our search for marine peptides good for the health of the ocean itself?

Kathelijne Bonne. This article is translated from the original in Dutch in the Belgian science magazine EOS Wetenschap (10/2026). Donate to GondwanaTalks. 

When we're ill, we pop a pill out of its blister pack and wash it down with a sip of water, barely giving it a second thought. If we even wonder where it came from, we probably picture a sprawling laboratory full of researchers in spotless white coats and safety goggles.

But a growing number of medicines is derived from marine organisms. A medicine might come from a predatory cone snail in the Pacific that paralyses its unsuspecting prey with venom. Or from sponges on a coral reef that filter litres of seawater; or from salmon scales. Any organism in the far corners of the ocean, where evolution has forced life to develop ingenious ways to survive, could be of interest.

In fact, there has never been a time when we did not exploit the ocean. Since time immemorial, we have drawn on its riches: fish, shellfish, pearls, whale oil, coral, algae, salt, minerals, petroleum, and manganese nodules. 

When it comes to life, in recent decades we have moved beyond simply studying the organisms themselves; instead, we are increasingly zooming in on the tiniest details—on microbiology, genes, and the molecules that make up these creatures, as well as the substances they produce. 

Perhaps the greatest discovery is just how rich the ocean is in molecules. Among the most promising are marine peptides, which are known for a wide range of biological effects, including anti-inflammatory, antimicrobial, antioxidant, antitumor, blood pressure-lowering, and antidiabetic effects.

The chemical repertoire of the ocean

'The ocean offers an enormous source of inspiration for the development of new medicines,' says Jana Asselman, professor of marine biotechnology at Ghent University and head of the Blue Growth Research Lab. 'Moreover, we have explored only a small fraction of the ocean's incredible biochemical diversity. Through millions of years of evolution, marine organisms have developed unique molecules to defend themselves, communicate, or adapt to extreme conditions.'

This is especially true for organisms that are sessile or not very mobile and can only defend themselves 'chemically', such as sponges, corals, sea anemones, medusae, and some algae. Moreover, every litre of seawater contains billions of microbes against which marine life must constantly defend itself. 

'Furthermore, the immune system of invertebrates such as sponges works differently from that of mammals and humans,' confirms Johan Robbens, marine molecular biotechnologist at the Institute for Agricultural, Fisheries, and Food Research (ILVO) in Flanders, Belgium. 'They lack the kind of adaptive immunity that uses antibodies like humans do. Instead, they rely on a range of defensive chemicals, including toxins. These defenses can contain remarkably diverse mixtures of molecules.'

Painkiller

'For example, the venom of the beautiful cone snail, Conus magus, contains a mixture of substances from which the peptide ziconotide was isolated. In humans, this peptide relieves severe pain. In 2005 it came on the market as Prialt,' says Steven Ballet, peptide expert and head of the organic chemistry research group at the Free University of Brussels (VUB).

A whole range of marine organisms is being studied for promising peptides

A whole range of marine organisms is currently being studied for promising peptides. These include sea cucumbers, sea squirts, pufferfish, krill, sea urchins, oysters, and all kinds of algae and microbes. Some 15,000 peptides from the ocean alone show potential. Every year, new promising marine peptides are discovered.

According to a recent review in the Chinese Journal of Natural Medicine on the growing potential of marine peptides, there is an increasing need for drugs that have fewer side effects and are better tolerated; or simply work better. 

In the lab, peptides from pufferfish, monkfish, peanut worms (Sipuncula), and scallops demonstrate remarkable anti-inflammatory effects. And with antibiotic resistance a growing concern, new antimicrobial compounds are a welcome development as well: icefish, scorpionfish, blennies, and nerite snails are just a few of the animals that contain peptides that kill bacteria.

And while peptides from sturgeon cartilage and pearl-producing shells act as antioxidants, peptides from sole, catfish, and green algae have been shown to kill cancer cells. This list is just the tip of the iceberg. A major stumbling block, according to the authors of this review, is purifying complex peptide mixtures to isolate the most effective ones. Even after that, the road to a box of pills you can pick up at the pharmacy is still a long one.

Monster from the depths

'The biological activities of peptides are indeed impressive,' Asselman agrees. 'However, most of the claims are still based on in vitro experiments or animal models. Most peptides don't make it to the stage of becoming a safe and effective drug. Often, you start with 5,000 to 10,000 interesting molecules in the lab. In preclinical research, only about 250 of those turn out to be worth pursuing. After clinical trials, perhaps only one effective drug remains.'

Sometimes the ocean simply gave researchers an idea. One of the world's most widely used peptide drugs was inspired by a marine molecule and developed independently of it. In the 1970s, there was a temporary moratorium on experiments with mice and other warm-blooded animals. As a result, researchers turned to marine organisms. A fisherman gave them an unlikely sea creature: an anglerfish that sometimes ended up as bycatch in the nets. With its spooky mouth and a lantern on its head, this deep-sea fish isn't exactly goodlooking. But what caught researchers' attention was its unusual pancreas. It played a key role in fundamental research into the hormone glucagon, which contributed to the discovery of GLP-1, a human-specific peptide that regulates hunger and satiety. Decades later, that knowledge helped lead to the development of the diabetes and weight-loss drug Ozempic.

Heart of the tuna

While the medical field primarily focuses on "exotic" species and invertebrates, the cosmetics industry has access to the enormous quantities of bycatch and waste material from the fishing industry. 'Only a small portion of all fish is used for human consumption,' says Robbens. 'Fish skins, heads, bones, guts, and scales are packed with proteins and other beneficial substances that can be valorised.' Since the cosmetics, food, and supplement industries are subject to less stringent regulations, peptides derived from collagen in fish byproducts are already being incorporated on a large scale into all kinds of products, including anti-aging products. For example, a peptide from the bulbus arteriosus, a small organ near the heart of the tuna, is a potential candidate as a dietary supplement against oxidative stress, or more specifically, against wrinkles.

However, one must be cautious about claims made by the cosmetics and nutraceuticals industries, as they sometimes ride the wave of the hype surrounding peptides. Clinically sounding names of peptides, combined with the "healing" image of the sea, quickly create the promise of miraculous effects. But these effects haven't always been proven.

Still, it pays to be cautious about claims from the cosmetics and nutraceutical industries, which sometimes ride the wave of hype around peptides. Scientific-sounding peptide names, combined with the sea's aura of healing, can make these products sound like miracle cures. The evidence for those claims is often less impressive.

Tonnes of sponges

'Fortunately, the search for marine peptides has a relatively small environmental impact,' says Asselman. 'It isn't driving demand for more fishing. In any case, that would be absolutely unsustainable, given the severe pressure marine ecosystems are already under. If commercial demand for a particular peptide led to targeted harvesting of wild organisms, such as marine sponges, that could quickly deplete wild populations. We've seen that happen before.'

'To develop peptide-based drugs, we don't need to pull vast quantities of marine life out of the ocean,' Ballet adds. 'Peptide research has one huge advantage. Once we've identified a peptide, we can either synthesize it in the lab or use microorganisms to 'grow' it. That way, we can develop marine peptides without putting additional pressure on marine biodiversity. Moreover, 'marine bioprospecting' isn't specifically focused on peptides. When an organism is studied, it undergoes a standard process to determine which substances it contains and what biological activities they perform. After that, we usually no longer need the organism itself.'

That's just as well, because to extract one gram of active peptide from a sponge, you'd need roughly one metric ton of sponges. However, certain sponges are sometimes grown, despite their slow growth. To study them, small pieces are cut off, and the sponge simply continues to grow.

'Waste streams from the fishing industry are partly used to extract high-value products such as collagen,' Robbens continues. "But for Belgium in particular, the waste streams are too small and too heterogeneous to derive added value from them, although we are investigating the potential applications. On the other hand, circularity and zero-waste are high on the agenda, although those concepts do not necessarily go hand in hand with eco-friendliness. The solvents used in processing are highly polluting, though progress is being made to reduce their impact.'

'So far, Belgian fishery waste has been purchased by companies from neighbouring countries and processed in bulk into fish meal, fertilizers, and biogas. In other countries, such as Norway – which has a big salmon farming industry – salmon byproducts are sorted into heads, skins, scales and bones right from the start, making the extraction of high-value products faster and more efficient. If the development of marine peptide-based products is having any impact at all, it lies primarily in how the peptides are purified.'

The ocean as a living library of molecules

'Artificial intelligence and synthetic biology are likely to become more important than traditional bioprospecting in the future,' adds Asselman. 'After all, using AI, we can search through vast amounts of genomic data, as well as numerous culture collections of marine organisms and databases of chemical compounds, without ever having to extract new organisms from the sea to develop new compounds.'

'When people ask what the real value of biodiversity is, I like to point to all the useful molecules the ocean contains – and why it's so important to preserve and protect that biodiversity. For example, we owe the ovarian cancer drug Yondelis to the ocean – and more specifically, to a sea squirt (Ecteinascidia turbinata). Perhaps the ocean also harbours the next cancer drug. Such connections make the concept of biodiversity more tangible. I prefer to view the ocean as a living library of evolutionary solutions. Our challenge is not to empty that library, but to discover, learn from it, and then translate that knowledge into sustainable processes and products – while ensuring that the library remains intact for future generations.'

Peptides are like Lego bricks

Peptides are organic molecules that perform a myriad of functions in the body. They are composed of amino acids – the small building blocks of life. Humans need about twenty different amino acids, although more exist. When a long peptide – consisting of roughly 50 amino acids or more – folds into a functional three-dimensional structure, you get a protein. You can think of amino acids as individual Lego bricks. The peptides are then Lego chains, and the proteins are finished structures. The number of amino acids, their sequence, and their folding allow for an unimaginable number of peptides.

The first peptide drug was insulin, which was an immediate breakthrough in medicine and has been in use for a century. Peptides can be derived from human, animal, plant, and marine sources, as well as from bacteria that live in symbiosis with these organisms. 'Roughly 40% of existing peptide drugs are natural products,' says Steven Ballet. 'Another 40% are inspired by nature. And 20% are entirely synthetic. This latter proportion is rising, mainly because AI now contributes to the design of peptides, although nature remains an indispensable source.' Goserelin is an important synthetic peptide inspired by a natural hormone. It is used in hormone therapy following prostate and breast cancer. Enfuvirtide, on the other hand, is a fully synthetic peptide used to against the HIV virus.

Looking for the ideal key: what makes peptides special

Many drugs work by binding to specific receptors and triggering or blocking a biochemical response. Peptide expert Steven Ballet compares this to a lock and key. The drug is the key, and the receptor it targets is the lock. The better the key fits and the more unique it is to a particular lock, the more effective the action. As Ballet explains, peptides can offer a middle ground between small-molecule drugs and larger protein-based medicines.

'Before the 1980s, most drugs were small molecules, such as paracetamol, which consists of 20 atoms. Small molecules are easy to make. Furthermore, they readily penetrate membranes to reach their target. And best of all, you can simply put them in a pill.' One good small molecule – and the very first drug derived from the sea – is the chemotherapy drug for leukemia, cytarabine. It was isolated from a sea sponge (Tectitethya crypta) and has been on the market since 1969.

'Starting in the 1980s, so-called biologics made their debut: large biomolecules with complex structures and shapes.' Take Keytruda, a widely discussed immunotherapy drug. A single molecule contains more than 20,000 atoms. 'Biologics are natural or nature-inspired molecules. They cannot be synthesized from simple starting materials but are produced biochemically. They have proven to be highly successful, which justifies their price tag. Thanks to their complexity, they interact flawlessly with a specific target. They have dethroned small molecules in terms of sales. But biologicals also have significant drawbacks. 'They are more fragile and harder to produce.'

Expanding the chemical space

'Peptides occupy the space between small molecules and biologics and are becoming increasingly popular because they offer the advantages of both. Because they are larger than small molecules, they make multiple contacts with the target and are therefore more effective. Although they are usually inspired by natural molecules, such as ziconotide from the cone snail, they can be synthesized in the lab.'

'We're constantly searching for the perfect key,' Ballet concludes. It's a bit like a puzzle that has to fit together like a game of Tetris. 'A small molecule acts like a jockey, fitting into multiple locks, which explains the many side effects. A large molecule is a unique but extremely expensive and fragile key. Peptides, on the other hand, are keys we can tailor to fit a particular lock. By tweaking natural peptides, we can fine-tune how they work and expand the 'chemical space' we can explore, opening up more possibilities for drug development.'

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