A new bull market is here ... almost. Some maintain that the S&P 500 has already begun a new bull market. Others, though, argue that the index must reach an all-time high first. Either way, many investors will want to have their short lists of stocks to buy at the ready.

Three Motley Fool contributors identified what they think are fantastic pharma stocks to buy in a new bull market. Here's why they picked Eli Lilly (LLY 1.19%), Novo Nordisk (NVO 0.84%), and Pfizer (PFE 0.55%).

Eli Lilly: Explosive growth potential

Keith Speights (Eli Lilly): Few big pharma stocks have more explosive growth potential than Eli Lilly. And it's not just potential -- Lilly is already delivering explosive growth. The drugmaker's shares have skyrocketed nearly 50% so far in 2023.

Lilly's revenue jumped 28% year over year in the second quarter to $8.3 billion. Several existing products helped drive this impressive growth, notably the breast cancer drug Verzenio, diabetes and heart failure drug Jardiance, and autoimmune-disease drug Taltz.

But Lilly's new products and others on the way hold the potential to kick the company's growth into an even higher gear. Mounjaro (tirzepatide) stands at the top of the list. The drug is already marketed in the U.S. for treating type 2 diabetes after winning approval last year. It raked in sales of more than $1.5 billion during the first half of 2023.

Lilly awaits U.S. approval of Mounjaro for chronic weight management. One analyst projects the drug could generate peak annual sales of nearly $69 billion. Even if it doesn't hit that level, Mounjaro seems likely to become the world's best-selling drug ever.

The U.S. Food and Drug Administration (FDA) expects to make an approval decision on Alzheimer's disease drug donanemab by year-end. If approved, the drug holds the potential to achieve peak annual sales in the ballpark of $7 billion.

Lilly also recently won FDA approval for Jaypirca in treating mantle cell lymphoma. It's waiting on approval to treat chronic lymphocytic leukemia as well.

If you looked only at Lilly's forward earnings multiple of 58.5, you'd think the stock is ridiculously expensive. However, I believe the company's tremendous growth prospects make it a bull market buy.

Novo Nordisk: An unstoppable stock that's worth a premium

David Jagielski (Novo Nordisk): In a bull market, investors are more willing to pay high multiples for growth stocks. One particularly enticing growth stock these days is Novo Nordisk. The big name behind weight-loss drug Wegovy and diabetes treatment Ozempic, Novo has established itself as a top healthcare company with a market cap now over $400 billion.

The biggest problem for Novo has been supplying enough of its drugs Wegovy and Ozempic. They have been in high demand over the past year, with consumers using the latter for weight loss even though regulators haven't approved it for that indication.

Novo Nordisk's revenue through the first half of 2023 rose 29% to nearly 108 billion Danish kroner. Wegovy's sales during that time have more than quadrupled to 12 billion Danish kroner, with Ozempic and Saxenda also generating strong year-over-year growth of 58% and 36%, respectively.

In August, Novo announced it was acquiring Inversago Pharma, a company that makes obesity drugs, for up to $1.08 billion to bolster its pipeline and capabilities further. Meanwhile, the company is also investing over $2 billion into expanding its manufacturing facilities in Denmark to help meet the huge demand for its products. Although the business is already growing robustly, Novo's growth rate could accelerate even further with the moves it is making.

Today, the stock trades at more than 40 times its trailing earnings. While that may be a steep multiple, it's arguably justifiable, given the opportunities in weight management and diabetes, two areas where there is a high need for ongoing care.

Novo's stock has risen more than 30% year to date. But with a lot more growth on the horizon for the business, it wouldn't be surprising for this stock to remain a hot buy in a prolonged bull market. Novo Nordisk should be an excellent investment for long-term investors, even with shares currently trading at a premium.

Pfizer: Too cheap to ignore

Prosper Junior Bakiny (Pfizer): To get the best bang for your buck in a new bull market, buying shares of undervalued companies might be a good idea. That's why investors might want to consider a drugmaker like Pfizer. The company's business isn't the most exciting in the world and it isn't breaking new ground in artificial intelligence or cloud computing. But it is reliable, and its products are always in demand.

Pfizer is in a downturn at the moment as its tailwind from coronavirus-related treatments slows. But this is likely to be temporary as the company has several regulatory approvals for important new products. These approvals include the RSV vaccine Abrysvo, alopecia areata medicine Litfulo, cancer drug Elrexfio, and Ngenla, which is used to treat pediatric growth hormone deficiency.

Thanks to its loaded late-stage pipeline, the drugmaker will continue adding new products throughout the next year. Pfizer has also been splurging on acquisitions. Its $43 billion buyout of cancer specialist Seagen is just the latest example.

Pfizer will have no problem with that big payout thanks to its success with its COVID-19 vaccine and medication treatment. The company's massive success over the past two years was arguably well worth Pfizer's current year of declining sales and earnings.

Despite an expanding portfolio of medicines, a deep pipeline, excellent prospects, and a strong dividend profile, Pfizer's forward price-to-earnings ratio is just 11, compared to 16.2 for the pharmaceutical industry. That makes Pfizer a fantastic stock to ride the next bull market.