The stock market sagged on Tuesday, so in the spirit of looking at the bright side of things, I've found a pair of stocks that rose notably despite the general sluggishness.

Both were up substantially on the day, with one even riding far into double-digit territory. Without further ado, here's a glance at both.

Two birds flying against the sun.

Image source: Getty Images

Biogen

Since the success of biotech stocks depends hugely on the pipeline of drugs they're developing, they can really get a lift from positive news about said treatments. And as with stocks in any other sector, they can also rise when they deliver better-than-expected quarterly results.

Well, guess what happened to Biogen (NASDAQ:BIIB) on Tuesday. That's right, it unveiled strong quarterly figures and some potentially excellent news about one of its drugs. No wonder its stock rocketed 26% higher on the day.

The pipeline news is what really got the market excited about the stock. Biogen announced it will seek approval from the Food and Drug Administration (FDA) for aducanumab next spring. This was a very pleasant surprise, as Biogen had halted testing of the Alzheimer's drug earlier this year following what seemed to be unsuccessful late-stage clinical trials.

Biogen said that it made its decision after it conducted a new analysis of the data from the trials that revealed more favorable results, and held discussions with the FDA. This is a very exciting prospect for the company, as Alzheimer's remains a daunting challenge for the medical community.

Meanwhile, Biogen drugs already in pharmacies -- notably spinal muscular atrophy drug Spinraza -- are selling well and providing a nice boost to the company's Q3 results, which were released early Tuesday.

For the period, revenue rose 5% on a year-over-year basis to $3.6 billion, while non-GAAP (adjusted) net profit saw a robust 13% gain to almost $1.7 billion, or $9.17 per share. Both line items compare quite favorably to the average analyst estimates of $3.54 billion on the top line, and $8.28 per share for adjusted net profit.

Tuesday's news dump provided optimism about both Biogen's current drugs on the market and the company's pipeline. But as always, caution is warranted in the biotech sector, where even the most promising drug candidates are not guaranteed to succeed in testing and ultimately win regulatory approval. So for me, particularly after Tuesday's price spike, Biogen is a wait-and-see stock.

Lyft

Lyft (NASDAQ:LYFT) didn't have quite the memorable day enjoyed by Biogen, but investors were still happy with its nearly 7% gain on Tuesday. 

The unusual rise in what has otherwise been a fairly disappointing stock since its March IPO was due to comments made by its founders on Tuesday. In a tech industry event in California, Lyft CEO Logan Green and President John Zimmer said that the company will flip to a profit by the close of 2021... at least on an adjusted, pre-tax operating basis.

Since analysts had predicted this ride into the black wouldn't happen before 2022 -- plus the words "Lyft" and "profit" rarely appear in the same sentence -- the market got excited about the comments.

Sure, a flip into some -- any -- kind of profit in the near future would be beneficial for the stock. And that new end-2021 target date seems achievable, given Lyft's strong and better-than-expected improvements recently in total ridership and average revenue per rider. Now that it's built up a fairly solid core of drivers and passengers, the company is also putting the brakes on certain discounts and incentives, which helps the fundamentals.

I remain skeptical about Lyft as an investment, though. Firstly, pre-tax operating profit is not net profit, the line item most stocks ultimately trade on -- and Lyft is deep in the red and projected to remain there for at least a few more quarters. Secondly, those improvements aside, the company operates in a business that is hotly competitive, and this competition keeps ride prices down.

Lyft aims to broaden its revenue base through subscriptions that would cover services other than rides. That's a fine and sensible idea, but we're far from being able to determine how viable this strategy will be. Finally, a recent law passed in California (a crucial market for the company) might sharply increase the company's labor costs.

So in spite of today's burst of enthusiasm, I'm still bearish on the prospects for Lyft stock.