What happened

Shares of Seattle Genetics (NASDAQ:SGEN), a pioneer in developing antibody-drug conjugates (ADCs) to treat cancer, soared 102% in 2019, according to data from S&P Global Market Intelligence. That performance made it one of the year's better-performing large-cap healthcare stocks. For context, the S&P 500 index returned 31.5% in 2019.

(In 2020, Seattle Genetics stock is down 1.7% through Jan. 10, compared with the S&P 500's 1.1% return.)

The hands of a person in a white lab coat mixing a liquid in a beaker on a surface that has other beakers and vials.

Image source: Getty Images.

So what

Seattle Genetics stock was roughly tracking the market until September. Then came several main catalysts that lifted off the stock.  

SGEN Chart

Data by YCharts.

On Sept. 28, the company released encouraging results of its phase 1 trial for EV-103 targeted at urothelial cancer, the most common type of bladder cancer. The next day it followed with an announcement of positive results from a phase 2 trial for its tucatinib drug, in combination with trastuzumab (Herceptin), in treating patients with HER2-positive colorectal cancer. Following the weekend release of these two announcements, shares rose 12.4% on Monday, Sept. 30.

On Oct. 21, shares popped 15.4% after Seattle Genetics announced positive topline results from its pivotal trial of tucatinib in locally advanced or metastatic HER2-positive breast cancer. The study compared using tucatinib in combination with trastuzumab and capecitabine to using trastuzumab and capecitabine alone. The company said it would submit a new drug application for this indication in the first quarter of 2020. 

Investors have been enthused about Seattle Genetics' prospects for some time, as this 10-year chart shows:

SGEN Chart

Data by YCharts.

Now what

2020 promises to be chock-full of news on the pipeline front for this promising biotech. While the company hasn't yet scheduled a date for the release of its fourth-quarter and full-year 2019 results, they should come out in early to-mid-February. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.