The marijuana industry is growing very rapidly, and marijuana stock investors have certainly taken notice.

According to Marijuana Business Daily's latest report, "Marijuana Business Factbook 2017," legal U.S. weed sales are expected to soar from a range of $5.1 billion to $6.1 billion this year to north of $17 billion by 2021. What's more, investment firm Cowen & Co. foresees $50 billion in legal U.S. sales by as soon as 2026. If legal cannabis continues to expand rapidly in North America -- Canada is considering a legalization of recreational marijuana, Mexico officially legalizing medical marijuana last week, and eight states in the U.S. having legalized recreational pot since 2012 -- anything is possible.

These marijuana stocks were unstoppable last week

This expansion has pot stock investors excited, and the two moves from marijuana stocks this past week are only going to add fuel to the fire. The so-called "budding stars" of the week were Cara Therapeutics (NASDAQ:CARA), which skyrocketed by 32%, and Insys Therapeutics (NASDAQ:INSY), which advanced a "tamer" 21%.

Let's take a look at what had these blooming pot stocks growing like a weed last week.

Cara receives a special designation from the FDA

The big boost from Cara Therapeutics came late in the week when it announced via an early morning press release that its most advanced experimental drug, I.V. CR845 (a kappa opioid receptor agonist, not associated with cannabinoids), had received the breakthrough therapy designation from the Food and Drug Administration (FDA) for the treatment of chronic kidney disease-associated pruritus (itching) in hemodialysis patients. In other words, because there's a significant unmet need in treating moderate to severe itching associated with CKD patients, and Cara's I.V.-administered CR845 generated positive results in part A of its phase 2/3 trial, the FDA has awarded a designation to Cara that may be able to expedite getting its drug to market. But please take note of the emphasis on "may" in the previous sentence.

The breakthrough-therapy designation will allow Cara to work more closely with the FDA to ensure there are no trial delays its ongoing phase 3 trial, and it may even help lop off roughly four months from its standard review process. However, dubbing an experimental drug as a breakthrough therapy does not mean it's guaranteed to be approved. It's a nice boost for Cara, but there are still no guarantees here, even with this designation.

What remains far more important for Cara is whether CR845 has success in far broader indications, such as pain treatment in the post-operative setting, and if CR701, a preclinical cannabinoid receptor agonist, has the potential to replace opioids as a broad pain treatment. Don't get me wrong: A special designation from the FDA is a good thing, but it may not be as good as the 32% pop last week would suggest until we have more answers.

The catalyst behind Insys' 21% run higher

For Insys Therapeutics, management changes appear to be the primary catalyst.

On Tuesday, June 20, Insys announced the addition of four pharmaceutical veterans to its management team. It really didn't matter, per se, where these industry veterans came from, so long as Insys made an effort to bring fresh faces in to distance itself from the still-ongoing Subsys debacle.

Allegations and lawsuits have been filed suggesting that up to 80% of Subsys prescriptions (Subsys is a sublingual medicine to treat breakthrough cancer pain that has nothing to do with cannabinoids) were being filled for off-label indications and that Insys' marketing may have been less than genuine. As a result, sales of Subsys have been effectively halved in two years, pushing the company to a quarterly loss from what was a healthy profit.

The addition of these industry veterans should help sweep away some of the company's bad PR, so it can instead focus on the upcoming launch of oral dronabinol solution Syndros as a treatment for chemotherapy-induced nausea and vomiting and anorexia associated with AIDS. If successfully launched into a highly competitive market, Syndros could be generating $300 million or more in peak annual sales.

Unveiling the Senate's health bill may be a catalyst, too

Additionally, Insys, and perhaps even to some degree Cara Therapeutics, may have benefited from the introduction of the Better Care Reconciliation Act in the Senate.

The Senate GOP bill made some sweeping reform suggestions from the previously proposed House GOP bill, known as the American Health Care Act. The bill extends both cost-sharing reductions and Medicaid expansion a few more years, removes the ability of states to applying for a waiver from the community rating, which is the waiver that mandates all people of the same age and location be charged the same premium, and moves back to income-based subsidies from age-based tax credits.

What this means for drugmakers is the strong likelihood that millions of low-income Americans should have a few extra years of coverage before their Obamacare-like subsidies are rolled back, assuming the Senate health bill has legs, which may be a bit of a stretch to say at this point. It also appears to have no provisions for drug-pricing controls, which is great news for drugmakers since pricing power drives profits.

However, when all is said and done, keep in mind that despite a great week for both of these aforementioned marijuana stocks, the federal government has dug in its heels on marijuana's schedule 1 status, and the inherent disadvantages of operating as a marijuana-based business don't look as if they're going to disappear anytime soon. In other words, the gains in Cara and Insys may prove short-lived if Congress doesn't loosen its federal regulations.