2 growth champions I'd buy and hold for two decades

In my opinion, the best companies to hold for the long term are those with a long runway for growth. Companies which have an enormous market to expand into are more likely to be able to continue to grow, especially when government-sponsored initiatives are providing a tailwind.

Indivior (LSE: INDV) and Harworth Group(LSE: HWG) are excellent examples. Indivior delivers treatments to help overcome opioid addiction, a severe problem the United States is currently facing, with speculation it could be the largest health crisis the country has ever seen.

Meanwhile, Harworth is working to become a major home builder in the United Kingdom. Both of these markets are huge and have political backing.

Policy makers in the US are beginning to take action on the opioid crisis, while UK policymakers are encouraging homebuilders to accelerate construction and meet rising housing demand.

Building for Britain

Harworth announced today that, as a continuation of its strategy to generate the most value for shoulders, it has acquired "four strategic sites across the North of England and the Midlands, for a total consideration of £45m plus acquisition costs." These sites include three separate parcels near Denby in Derbyshire with the potential to build up to 3,000 new homes and 450,000 sq ft of commercial space.

As Harworth continues to build its presence in the housing market, I believe the company could generate tremendous returns for investors, especially as the government continues to devote money in time to helping developers build new homes.

And right now, shares in the business look cheap, trading at a price to book value of only 0.9. According to the last set of available figures, the book value per share is 129p, indicating an upside of 14% as the company continues to grow. At present, the shares only support a dividend yield of 0.8%, although I expect this to rise steadily in the years ahead as Harworth's current building plan gets underway.

Fighting addiction

Today's figures from Indivior, for the first three months of the year, are disappointing. But it's the company's future of potential I'm excited about.

Excluding the impact of one-off items, net income declined 3% to $78m in Q1 as revenue fell 6%, thanks mainly due to competition. However, this year the company is introducing its new Sublocade opioid treatment to the market. Launched during the first week of February, initial indications show that this treatment could be a "transformational tool in the fight against the opioid epidemic", according to Indivior CEO Shaun Thaxter.

The introduction of this product is expected to lessen the group's reliance on sales of legacy products, which are coming under attack from generic competitors. And even though earnings are expected to decline over the next two years, as Sublocade sales gain traction and more money is devoted to fighting the opioid epidemic, I believe Indivior's earnings weakness should not last.

It may take some time, but I think that this is one company worth watching over the next decade as the war against opiate addiction gains traction. There's also the possibility Indivior will succumb to a takeover if a larger peer wants to get its hands on the firm's intellectual property.

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Rupert Hargreaves owns no share mentioned. The Motley Fool UK has no position in any of the shares mentioned. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.