2013 was a banner year for the health care industry, as major companies introduced new treatments capable of substantially improving the lives of patients.

Let's take a look back at three of the top health care advances in 2013 and the companies that achieved them -- Halozyme (HALO 0.39%), Roche (RHHBY -2.24%), ImmunoGen (IMGN), and Gilead Sciences (GILD 0.07%).

1. Halozyme turns IV drips into single shots
Halozyme, the maker of the rHuPH20 human recombinant enzyme more commonly known as Enhanze, is a polarizing stock. The bulls believe that its technology, which helps drugs break through the hyaluronic acid in the skin, will revolutionize health care because it can convert intravenous drugs into subcutaneous ones.

In other words, Enhanze can turn slow IV drips into fast-acting, single shots. Meanwhile, the bears believe that Halozyme's technology could trigger an immune system response, causing antibodies to attack the injected treatment.

Earlier this year, ViroPharma (NASDAQ: VPHM) (recently acquired by Shire) canceled a phase 2 trial for a subcutaneous version of its hereditary angioedema, or HAE, drug Cinryze using Halozyme's Enhanze technology when patients unexpectedly developed antibodies against the drug. Shares of Halozyme fell as investors wondered if the bears had been right all along.

However, in September Halozyme's partnership with Roche bore fruit -- the subcutaneous version of Roche's top-selling breast cancer drug, Herceptin, was approved in the EU. Herceptin is a lab-created antibody which specifically targets the overexpression of HER2 (human epidermal growth receptor 2), which occurs in approximately 20% of breast cancer cases.

Herceptin SC (subcutaneous) was a major advance for breast cancer patients, since it reduced the typical IV treatment time of 60 to 90 minutes down to only 2 to 5 minutes with a simple shot. Looking ahead, Roche is also working with Halozyme on a subcutaneous version of Rituxan/MabThera, its blockbuster drug for blood cancer and autoimmune disorders.

2. ADCs take center stage
The second major advance this year can also be credited to Roche, which brought the second ADC (antibody-drug conjugate) to the market in 2013.

ADCs are lab-created monoclonal antibodies which are injected with toxins. Once the monoclonal antibody finds the cancer cell, it links to the cell and injects it with chemotherapy toxins, killing it from the inside. In other words, ADCs are "cancer smart bombs" which can kill cancerous cells while sparing healthy ones.

Roche's ADC Kadcyla, developed by ImmunoGen, enhances its breast cancer drug Herceptin with a toxin. The result is a drug that "triple kills" a cancer cell -- it binds to the cell's surface to block out growth signals, makes the cell visible for the immune system to destroy, then injects it with toxins to insure its destruction.

Kadcyla was approved by the FDA in February and by the EU in November. The only other approved ADC on the market is Seattle Genetics' Adcetris, which treats blood disorders.

The approval of these two ADCs are key developments in oncology, since they could replace traditional chemotherapy, which kills both cancerous and healthy cells -- resulting in side effects such as hair loss, fatigue, anemia, and gastrointestinal problems.

3. Gilead Sciences revolutionizes hepatitis C treatments
Although 2013 was a huge year for cancer treatments, Gilead Sciences also revolutionized hepatitis C drugs with the FDA approval of Sovaldi in December. More than 3.2 million people in the United States are estimated to have hepatitis C, which can lead to liver failure and cancer if left untreated.

To understand why Sovaldi was such a huge leap forward, we need to understand how hepatitis C was treated in the past. The most commonly used drugs were ribavirin, an older antiviral drug, and interferon, which activates the immune system but can cause severe flu-like symptoms. Hepatitis C drugs were also usually injected.

By comparison, Gilead's Sovaldi is a once-daily pill that can be taken, in some cases, without an additional dose of interferon. Patients with genotypes 2 and 3 of the hepatitis C virus can simply take Sovaldi with ribavirin without interferon. However, patients with genotype 1, the most common form of the virus, and type 4 must still take Sovaldi with ribavirin and interferon.

While not a perfect all-in-one oral hepatitis C drug, Sovaldi is a big step toward interferon-free treatments, which could eventually propel the drug to annual peak sales of $3.8 billion.

Gilead Sciences, however, has been criticized for the pricing of the drug. A full 12-week treatment of Sovaldi will cost a whopping $84,000, or $1,000 per pill. By comparison, Johnson & Johnson's Incivek/Incivo and Olysio, which are not part of interferon-free drug regimens, both cost approximately $66,000 for 12-week treatments.

The Foolish takeaway
These accomplishments from Halozyme, Roche, ImmunoGen, and Gilead Sciences represent the three top health care advances this year, in my opinion.

Of course, there were plenty of other medical accomplishments this year -- such as Biogen Idec's multiple sclerosis drug Tecfidera, Johnson & Johnson's diabetes treatment Invokana, and Medtronic's wearable artificial pancreas -- that are also worth keeping an eye on.

So, dear readers, what would be your picks for the top health care advancements in 2013? Please let me know in the comments section below!