Despite everything that has happened so far this year, major indexes are trading near record highs once more. While a rising tide lifts all ships, it can be a bit trickier for investors to single out the most promising companies from the rest of the businesses out there on the market.

One industry that has more than its fair share of good bets is the pharmaceutical industry. The prospect of developing a COVID-19 treatment certainly has helped the companies that are involved in that work. However, many that aren't involved in COVID-19-related work have still seen impressive results so far in 2020.

Here are three pharmaceutical companies that have done well so far this year and are poised to do even better going forward.

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1. Vertex Pharmaceuticals

Vertex Pharmaceuticals (NASDAQ:VRTX) has proven to be one of the most resilient pharmaceuticals on the market, with shares rising 27.3% since the start of the year. While there are a few reasons for this, Vertex's main advantage is its cystic fibrosis treatments.

A condition that causes potentially life-threatening buildups of mucus in the lungs and digestive tract, cystic fibrosis (CF) affects about 70,000 people around the world, with approximately 1,000 new cases being diagnosed each year. Vertex already had three separate treatments for this condition -- Orkambi, Kalydeco, and Symdeko/Symkevi -- but the most promising is its new drug, Trikafta.

In Vertex's second quarter, Trikafta brought in an impressive $918 million in revenue. That's a 219% increase from the $420 million reported in the fourth quarter of 2019, when the drug received U.S. Food and Drug Administration (FDA) approval and became available for purchase. Despite being such a new drug, Trikafta already accounts for the majority of Vertex's product revenue at present.

Many other treatments for CF, such as inhaled mucus thinners, just address the symptoms rather than the disease itself. Given this, Vertex enjoys a very strong position in this market with its cadre of CF drugs, something that seems unlikely to change anytime soon.

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2. AstraZeneca

The only coronavirus vaccine maker on this list, AstraZeneca (NYSE:AZN) is definitely one of the leading names in the race to develop a vaccine. The company teamed up with the University of Oxford to develop and distribute a new vaccine candidate earlier this year, with 400 million doses set to be produced by the end of 2020.

Even putting a potential vaccine aside, AstraZeneca still has a lot going for it. That's mainly thanks to the company's lineup of new potential blockbuster drugs, which are experiencing tremendous growth. Quarterly revenue for AstraZeneca's top three cancer drugs, Tagrisso, Imfinzi, and Lynparza, is up 32%, 46%, and 48%, respectively, compared with the year-ago quarter.

In fact, Tagrisso just crossed the billion-dollar mark in sales during AstraZeneca's second quarter. Imfinzi and Lynparza brought in $492 million and $419 million this quarter, respectively. AstraZeneca's second best-selling product is an inhalable asthma and lung disease treatment called Symbicort. While it's not growing as fast as some of AstraZeneca's other drugs, sales for Symbicort are up a respectable 12% in Q2 to $653 million.

AstraZeneca also has an incredibly large candidate pipeline, so the potential for further blockbusters down the road remains high. At present, the company has 166 projects in clinical development, with 24 of them currently undergoing phase 3 trials. Even if just one or two of these new candidates takes off, this could translate to billions of dollars in extra revenue for AstraZeneca.

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3. GW Pharma

GW Pharma (NASDAQ:GWPH) is one of the rare examples of a pharmaceutical company developing treatments using cannabis-based compounds. The most famous of these is Epidiolex, a cannabidiol (CBD)-based drug that treats two types of childhood epilepsy known as Dravet syndrome and Lennox-Gastaut syndrome.

First-quarter revenue grew to $120.6 million, with $116.1 million of this figure coming from Epidiolex sales. For context, GW had just $39.2 million in quarterly revenue at about the same time last year.

Another thing that has some industry experts excited about GW Pharma is its second upcoming potential treatment. Nabiximols is a different CBD-based drug that helps patients who have multiple sclerosis (MS) deal with a common symptom known as spasticity. Affecting about 80% of all MS patients, spasticity often causes stiffness in the legs and arms, painful spasms, and a general difficulty in controlling one's muscles.

Considering that close to 1 million people in America alone have been diagnosed with some form of MS, GW Pharma could be entering a major market should Nabiximols become a success. The drug is about to begin phase 3 trials in the U.S., but has already seen positive results in non-U.S. clinical trials; it's actually already been approved in the U.K. under the name Sativex.

Having already hit one financial home run with Epidiolex, GW Pharma could find itself with a much larger success in the form of this second CBD drug. While nothing's certain in the world of clinical drug development, GW Pharma's odds right now are looking pretty good.