Drug developers have grown their horns thanks to a recent boom in venture capital, a virtuous cycle in which investors poured millions into months-old startups with the promise of lucrative initial public offerings or big-ticket buyouts. But for many, going public at a multibillion-dollar valuation just isn’t feasible in the short term. And returning to the well of venture capital would probably require selling new shares at a price below the last ones, a prospect investors dread.

So how do you stop your unicorn from devolving into an everyday pony?

If these companies — including Moderna Therapeutics and Intarcia, valued at more than $5 billion each — can’t live up to the hype, industry insiders worry that biotech might quickly catch sight of its shadow.

“The sector will suffer,’’ said Jeremy Levin, the chief executive of Ovid Therapeutics. “Any one technology base that makes over-reaching promises sees its sector suffer when those promises do not come true.’’

He has seen it happen before.

In the millennial fervor around the mapping of the human genome, otherwise reasonable people briefly believed a drug for just about everything lurked around every double-helixed corner. That helped a slew of biotech startups, including Human Genome Sciences, reach unheard-of valuations.

Levin recalls an illustrative slide in that company’s IPO presentation, reading, simply: “Genes = $.’’

That equation ended up being quite a bit more complicated, and when the so-called genomics bubble burst in the early 2000s, biotech endured its version of the dot-com crash. Investors lost fortunes. Startups went out of business. And the lasting effects cast a shadow over the industry for nearly a decade.

Now biotech risks doing it all over again, as a generation of companies that made glittering promises faces the prospect of failure.

Just like Uber and WeWork before them, biotech’s most-discussed unicorns are facing a difficult situation: They need to raise more money eventually, but the traditional paths to funding are too narrow for their bloated valuations.

Moderna, which has raised more than $2 billion from private investors, is burning through about $450 million a year. Intarcia had a logical route to the public markets right up until the Food and Drug Administration rejected its lead product last year, a surprise that seemed to scatter its best- laid plans. (Neither company responded to a request for comment on plans for the future.)

And they’re not alone: There are eight private biotech companies with valuations exceeding $1 billion, according to CB Insights, a number that analysts expect will only grow as VCs put more and more money into generations of upstarts.

“There’s going to be some really big acquisitions or some really big burnouts, because the valuations are quite large right now,’’ said Chris Haskell, who scouts for biotech partnerships at pharma giant Bayer.

But there could be a third path for biotech’s tottering unicorns: If you have Uber problems, consider an Uber solution.

The last two times the ride-hailing company needed money, it didn’t go public or make the rounds with VCs. It went to the trillion-dollar Saudi Arabia sovereign wealth fund and the Japanese telecom giant Softbank, which has earmarked $100 billion for investments.

Long derided as “dumb money’’ by specialist investors, the Saudis and their ilk used to place bets by giving their money to VCs and hoping for the best. Now they’re increasingly cutting out such middlemen and putting money directly into individual companies.

The practice is commonplace in tech, and it’s gradually emerging in biotech.

The Alaska Permanent Fund, shepherded by the venerated VC Arch Venture Partners, has since 2013 invested in a spate of biotech startups including Juno Therapeutics, Denali Therapeutics, and Codiak Biosciences (mountaineering is a theme).

Softbank made its first biotech investment last year, participating in a $1.1 billion round for Roivant Sciences and cosigning the company’s quest to find hidden gems in the pipelines of other drug makers.

For biotech startups, the allure is clear. Going public is a chore. There are bankers to pay, lawyers to retain, and laws that force you to tell the world — and your competitors — just what you’re up to in all those labs. If superlatively wealthy investors are willing to give biotech companies the money they need, why not take the Uber route and stay private?

But the marriage of biotech and overseas moneymen may be rockier than expected.

For one, drug development is a daunting proposition for any investor, let alone one without scientific expertise. The case for an app that makes a car appear at your door is fairly simple to make. Explaining how to get synthetic mRNA past hungry Kupffer cells and into the mouths of macrophages probably takes a few more slides.

Then there’s the cultural divide. If you’re a biotech on Softbank’s radar, you’ve probably taken some VC money, and VCs like to invest according to a schedule. After about seven years, VCs need an exit — either a sale of the company or an IPO that lets them liquidate shares on the open market — so that they can pay their investors and get to work raising the next fund.

The Softbanks of the world don’t have the same restrictions, and that could make for strange bedfellows on the board of any VC-backed biotech company that brings a sovereign wealth fund into the fold. If one member of your board is operating on a VC schedule and another is an oil-rich sultan who could misplace the GDP of a developing nation in his couch, there could be disharmony.

All that said, the money only matters if its recipients can actually develop a drug that wins approval, Levin said.

And valuation is “just one guy convincing another guy to pay for something,’’ said Tillman Gerngross, CEO of Adimab, a $3 billion private company with no ambitions to go public.

“In biotech, you either sell dreams or you sell data,’’ Gerngross said. “It’s that simple.’’

Damian Garde can be reached at damian.garde @statnews.com. Follow him on Twitter @damiangarde. Follow Stat on Twitter @statnews.