Humans have been chasing longer and stronger erections for centuries. From ground-up ants and "Spanish flies" to modern drugs, men hope to bring back some magic into a cocked-up sex life. How far would you be willing to go for an erection? Would you take a drug made from genetically modified spider venom? Medical researchers think that will be the next big thing to.... make things bigger.

ED Is a Problem That's Growing

Erectile Dysfunction (ED) has a wide range of causes; some of the most common are diabetes and prostate surgery, as well as just plain old getting old. ED affects about 10 percent of men in each decade of life. Cumulatively, that adds up to a lot of dudes with occasional erection problems (40 percent of men in their 40's, 50 percent of men in their 50's, etc.).

All ED drugs on the market are phosphodiesterase (PDE5) inhibitors, which work by making muscles in a penis relax. This seems counterintuitive unless you have a firm grasp on how the plumbing of a penis works.

During arousal, valves controlling blood flow into the penis slacken, allowing gravity to fill the penis with blood. This creates internal pressure, so the penis becomes firm. The erection lasts as long as the valves stay open, and this is controlled with a complex series of chemical reactions.

Those chemical reactions are what ED drugs manipulate. Unfortunately, about one in three men taking ED drugs currently available are not helped; and of course there is the occasional side effect of blindness. Enter the Spider.

__Is That a Banana Spider, or Are You Just Glad to See Me? __

Brazilian Wandering Spiders, or Banana spiders (Phoneutria nigriventer) are big: over a 5 inch leg span, or 13 cm. They hunt nocturnally in tropical forests, usually bothering no one except the small animals they eat. They have a reputation that is as as oversized as their body; these spiders rarelytravel on bananas, despite their name.

In case studies of 422 Brazilians bitten by these spiders, >90 percent of the bites weren't medical emergencies. The most common symptoms were pain, sweating, and elevated heart rate. So why are banana spiders so notorious? In a few rare cases, their bite causes priapism. Destin described it well in this video: "Priapism is a medical emergency involving the penis which is terrifying."

Penises are not supposed to have blood pooling in them for hours at a time. When blood stops circulating, it begins to coagulate and clot. One's penis is not a good place to develop congestion. Needles, and sometimes scalpels, are involved in fixing that problem.

Researchers working to identify naturally-derived chemicals that might help with ED noticed the reports of priapism. And that's how the path to GMO Spider Viagra began.

Seminal Work in Spider-Caused Erections

This cross section of a penis shows the corpus cavernosa, the spongy "meat" of a penis that fills up with blood during an erection. This is the part researchers were cutting out and hooking up to electrodes. Licensed under Public Domain via Wikimedia Commons

The first thing I learned working on this article was that every single research paper I read on this topic made me cringe. And I don't even have a penis.

Much of the research on ED is done on "cavernosal strips" – tissue samples taken from rodent penises. Or, occasionally, tissue from human penises.

The second thing I learned working on this article is that emailing researchers to ask how they obtained human penis tissue for their research won't go well. None of them returned my emails or phone calls. I can't really blame them – if a random woman emailed me to ask where she could acquire human penis parts, I probably wouldn't reply either.

Fortunately, mouse researchers were slightly more forthcoming about their methods. Essentially, you cut off the penis of a (recently deceased!) mouse, and hook up the relevant bits to an electrical stimulator. Once you have your penis chunks sliced out and connected, you can directly measure the contraction of the smooth muscles in corpus cavernosa tissue when you apply different chemicals.

And so, in a series of elegant experiments, PnTx2-6, the active compound in wandering spider venom, was confirmed as a biological version of Viagra. Even better, it appears to have fewer side effects than existing ED drugs (in mice, anyway). Once the usefulness of wandering spider venom was conclusively demonstrated, the next problem became how to make enough of it to conduct clinical trials.

GMO Spider Viagra

For obvious reasons, farming large numbers of giant spiders for toxic venom isn't a commercially viable proposition. A synthetic way to make lots of a biological product already exists for drug creation. By harnessing genetically modified bacteria, we now grow insulin, tissue plasminogen activator, and human growth hormone in commercial quantities. GMO drug production is not new.

In 2014, researchers successfully created a recombinant baculovirus with the PnTx2-6 gene. They then used this to infect a culture of caterpillar cells which produced the spider toxin.

The researchers then tested it on rats with "bilateral cavernous nerve crush injury." It's a rat model used to research damage from prostate surgery, and yes, it is as awful as it sounds. They were able to significantly restore corpus cavernosum blood flow with their recombinant spider venom.

__What's next? __

Don't expect to see this drug in your doctor's office anytime soon. Now that scientists can make larger quantities of the chemical, trials to determine the toxicity and efficacy of the drug in humans will still take years. Right now, we only know how to give mice and rats (and amputated human penises) a stiffie with PnTx2-6.

A larger question is will anyone take a drug that made from spider venom produced by genetically modified cells. Consumers are wary of GMOs, although most are willing to accept genetically modified products if they have a clear benefit.

While I've been having fun with my penetrating analysis of the data here, 1 in 14 men over age 60 will develop prostate cancer, which has ED as a common side effect of treatment or surgery. It's a real quality of life issue. With sales of over $4 billion yearly for Viagra and Cialis, it seems likely that this compound will continue in the drug pipeline, because it does have real potential to both improve erections and generate a profit.

I eagerly await the cross-marketing campaign featuring SpiDurex condoms.