When it comes to safe stocks, there may be none safer than healthcare conglomerate Johnson & Johnson (NYSE:JNJ). Johnson & Johnson is often a staple holding for income seekers, conservative investors, and even value investors. It has a 54-year streak of increasing its dividend payout, which should almost certainly become 55 years come April, and it's one of two remaining publicly listed companies with a "AAA" credit rating from Standard & Poor's. That's a higher credit rating than the U.S. government.

The secret to J&J's long-term success has been its business structure. Instead of operating as one giant company, it's composed of more than 250 subsidiaries, which allows management to play with the dominoes, if you will, from time to time, in order to boost growth. It's been able to divest slower-growing assets and acquire pharmaceutical products in recent years to boost its near- and intermediate-term growth prospects. Pharma is, without question, the largest contributor to its gross margin and top- and bottom-line growth.

Increasing stacks of pills next to a bottle atop cash, symbolizing growing drug sales.

Image source: Getty Images.

Remicade woes take shape

However, J&J might have a big problem on its hands. Its top-selling drug, Remicade, an anti-inflammatory treatment for a host of diseases, is facing competition from the recently launched Inflectra, a biosimilar drug developed by Celltrion and marketed by Pfizer at a 15% discount to Remicade's list price. Sales of Remicade stumbled by nearly 2% in the U.S. during the fourth quarter, signaling that sales of J&J's nearly $7 billion drug could begin to head in reverse.

For its part, Johnson & Johnson recently announced the pricey $30 billion acquisition of Actelion (NASDAQOTH:ALIOF), a Swiss-based developer of specialized lung-disease drugs to help immediately stem the pain from lost Remicade revenue. Actelion's Opsumit and Uptravi are each expected to generate in the neighborhood of $2 billion in peak annual sales.

The Actelion transaction, however, may not have even been necessary if J&J hadn't been catering to the short-term mind-set of Wall Street. In fact, J&J may have its Remicade replacement already in hand.

Johnson & Johnson already has its Remicade replacement

Box and vial of Remicade.

Image source: Johnson & Johnson.

Earlier this week, Danish drugmaker Genmab reported its full-year results and noted that multiple myeloma drug Darzalex, which is marketed by Johnson & Johnson, is fully on track to generate $1.1 billion to $1.3 billion in full-year sales in 2017. The drug wound up generating $572 million in sales in its first full year following its approval in Nov. 2015. Genmab is entitled to receive tiered royalties on the sale of Darzalex, and guided analysts to expect $132 million to $156 million in milestone payments this year based on the aforementioned $1.1 billion to $1.3 billion in expected sales.

While the expected doubling in Darzalex's sales might wow you, the drug appears to just be getting started. According to Genmab CEO Jan van de Winkel in an interview with Reuters, in a utopian scenario where Darzalex expands into other blood cancer indications, and perhaps even solid tumors, it could generate as much as $13 billion annually in peak sales. Van de Winkel believes that Darzalex could "definitely" generate $9 billion in peak annual sales, which for J&J would mean replacing every cent Remicade is currently providing (if not more).

Multiple myeloma is a growing market for nearly all

Multiple myeloma diagnoses have been on the rise, largely as a result of refined methods of detecting the disease earlier, which, for investors, means that the size of the pie for large multiple myeloma players -- Genmab/J&J, Celgene, and Amgen -- is growing. The duration of treatment for multiple myeloma patients has improved as well, which is largely a testament to the improved tolerability and outcome of next-generation medicines. This would also mean strong pricing power for these drugmakers, too.

Box and vial of Kyprolis.

Image source: Amgen.

With Darzalex mostly dominating the third-line and higher dosing, and being administered in combination with Revlimid, it's really of no danger to Celgene's beast of a multiple myeloma drug.

However, Darzalex may be a bit of a concern for Amgen's Kyprolis. Though the two drugs have never gone head-to-head in clinical studies, they did face very similar circumstances in the phase 3 studies that led to their third-line and up multiple myeloma approvals with the Food and Drug Administration. Both drugs treated patients who'd progressed on an average of five prior lines of therapy, but Darzalex delivered a 29% objective response rate compared to Kyprolis' 23%. Again, this is pure coincidence and not causation at work here, but this trial data could be coercing physicians and patients to choose Darzalex over Kyprolis.

Mid-single-digit growth is very achievable

For companies the size of J&J with nearly $72 billion in annual sales, mid-single-digit sales growth is something quite exceptional and hard to come by. However, with J&J shifting its business over the past couple more toward pharmaceuticals, it's becoming very achievable.

Johnson & Johnson outlined plans in May 2015 to file 10 novel drugs for approval with the FDA by 2019 that had the potential to reach at least $1 billion in peak annual sales. Darzalex was just the first of that bunch to get approved. If its first drug has "definitely" $9 billion in peak annual sales potential according to Genmab's CEO, imagine what the remaining nine drugs could do for its top and bottom lines.

My suggestion would be to stop worrying so much about Remicade because J&J may already have a Remicade revenue replacement ready to rock n' roll.

Sean Williams has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Celgene. It also recommends Johnson and Johnson. The Motley Fool has a disclosure policy.