Over the course of The Motley Fool's 26-year history, one of its guiding principles has been to look for the positive side of the story. The best stocks, services, and stories have produced some of the best returns for investors. Those innovators don't always pay off fast, but that's OK -- when you buy and hold for the long term, you can afford to be patient. And speaking of patience ... or rather, of patients, it's time for Rule Breaker Investing host David Gardner to pick another of his five stock samplers, and this time, his theme is medical miracles. Each company he's recommending has big potential to cure a condition that has thus far been incurable, or to create new possibilities where none existed before.

By definition, that means that his picks this time may carry more risk than some of his prior recommendations. For every biotech breakthrough that makes it to market, there are many "promising candidates" that don't pan out. Still, three years from now, the Motley Fool co-founder expects that on the whole, this basket of stocks (all of which are all already active recommendations in his portfolio) will be beating the S&P 500 -- and saving lives, too.

Recommendation No. 2: gene therapy specialist bluebird bio (BLUE 5.93%), which has a relatively small market cap in the pharmaceutical world, but it has big goals. Using various cutting-edge technologies, including the extremely promising CAR-T therapies, it hopes to alter the genetic makeup of patients to cure them of severe genetic and rare diseases, including some cancers.

A full transcript follows the video.

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This video was recorded on April 3, 2019.

David Gardner: Stock No. 2: bluebird bio, BLUE. If you ever check their website or their branding, you'll see it's one of those companies that decided not to use capital letters for its name. It's going all lower case with bluebird bio. That might endear it to some of you. It kind of suggests some humility or a little bit of right-brain thinking on the part of at least the branding people at bluebird bio. I kind of like it! It's distinctive.

Amgen, which I just presented to you, has a market cap -- which I know you know, we've made a game show of here on this podcast, so this is important -- Amgen's market cap is around $120 billion or so, a little bit over that right now. bluebird bio, by contrast, has a market cap of $9 billion. I'll mention that for each of the companies so you have a sense of their size. bluebird bio is less than one-tenth the size or value of a behemoth like Amgen. Yet, still, $9 billion isn't bad for a relatively recent company that is probably the main representative of gene therapy among all of my stock selections in Rule Breakers and Stock Advisor.

I first picked bluebird bio in January of 2015. It was at $95 then. By June of 2017, two and a half years later, it was at $109. I decided I'd re-recommend it again. It'd gone from $95 to $109. Today, it's $161. I really am glad that the future was already there. It just wasn't evenly distributed. We took advantage of our knowledge and appreciation of the potential of gene therapy, and certainly bluebird bio in its own way, early stage, has been cashing in on some of that potential. It's been a winning stock. It's one of those where we recommended it, it goes up, we recommend to buy some more, that goes up. That describes -- I know you know this -- how we approach investing generally as Rule Breakers.

Two things I like about bluebird bio. The first is, as I just mentioned, it's the main representative of gene therapy among all of my selections. This company is very focused on gene therapy. Now, I don't want to toss around a phrase like that and not have everybody come along with me in terms of their understanding. I know some of you are working in gene therapy, and know it about 73 times better than I do. For those who don't understand what the phrase means, it is the therapeutic delivery of nucleic acid -- that's kind of what makes up your DNA -- it's the therapeutic delivery of nucleic acid into a patient's cells as a drug to treat disease. Basically, we're altering the genetic makeup of people in order to cure them. Now, of course, any powerful technology like this can be used for good or for evil. It's kind of like the internet. There are people doing bad things on the internet. But I personally think, take it all in all, the internet has been a completely capital-A awesome development for all of us over the last 30 years.

Quick note to self. I listened to our mailbag episode last week, and I decided that I said awesome too much. I think I over-rely on that word. I'll try not to use it. I just used it. I'll try not to use it again this podcast.

Alright, now back to bluebird bio. Altering your genetic makeup. What does bluebird bio focus on? It's looking at severe genetic and rare diseases. It's trying to introduce a technology that can get better DNA into you to cure you of that disease.

Thing No. 2 that I like about bluebird bio, it is very focused on CAR-T immuno-oncology. Now, this isn't the only company in our stable that has a focus on CAR-T. As I do this podcast on YouTube, as a visual, you can all see that I'm about to give you what that stands for without looking at my notes to show that I have actually embodied this in my head now: chimeric antigen receptor therapy. That therapy has been a fairly miraculous recent development. As it turns out, you can take blood out of you or me, improve it, process it, put it back in us, and start to help with some forms of cancer. President Jimmy Carter has benefited from this. There's some other higher-profile people who've been fully cured, or at least cancer's gone into deep permission so far as we can tell through this chimeric antigen receptor technology. We're talking about a company that uses your own immune system, your T cells, to fight back against a cancer that you might have in you. And yes, bluebird bio is focused right there with a lot of its efforts. That's another thing that I like. In an age where cancer immunotherapy looks like not just the next big thing, but a significantly big thing right now that's going to get bigger, I really like bluebird bio's positioning.

What's one thing to watch with BLUE? Well, here's a fun one. This company does not even have an entry on Wikipedia. I can look up almost any company that I've recommended on any of my portfolios, even lesser known companies, and they've got a Wikipedia entry. But bluebird bio... let's keep watching. At some point, someone's going to start a page for bluebird bio on Wikipedia. But this is a $9 billion company that apparently is under the radar still, enough that nobody has even thought to create a Wikipedia page for bluebird bio. So, there's something to watch.

Now, of course, I'm having fun with that, but it does suggest to me that the future is already here, but awareness of it is clearly not being very evenly distributed. I think, just as I first recommended the stock more than four years ago, and it's been a big winner for us, I think it's still early stages for a company like this. We'll see.