College football isn't the only thing that kicked off in style in September. Quite a few biotech stocks enjoyed kickoffs of their own over the last week.

Three of the biggest winners were ProQR Therapeutics (NASDAQ:PRQR), MannKind Corp. (NASDAQ:MNKD), and Arrowhead Pharmaceuticals (NASDAQ:ARWR). Here's why these biotech stocks soared this week and a look at whether they're smart picks for investors now.

Businessman holding cell phone with line chart going up and dollar signs in foreground

Image source: Getty Images.

1. ProQR Therapeutics: The eyes have it

Shares of ProQR Therapeutics skyrocketed 107% this week. The clinical-stage biotech announced interim results on Wednesday from a phase 1/2 clinical trial of experimental drug QR-110 in treating Leber congenital amaurosis type 10 (LCA10), the leading genetic cause of childhood blindness. 

ProQR reported that 60% of patients in the study experienced a clinically meaningful response in both visual acuity and ability to navigate a mobility course after three months of treatment. The biotech stated that a secondary analysis showed that the improvement continued beyond the initial period of treatment. QR-110 also appeared to be well-tolerated with no serious adverse events reported.

These results were so positive that ProQR is stopping enrollment in the study and plans to advance to a pivotal phase 2/3 clinical trial in the first half of 2019. The company had also originally planned to administer a higher dose of QR-110 to patients in the phase 1/2 study but opted not to do so after similar effects were observed in two lower doses.

2. MannKind: United it stands

MannKind stock zoomed 61% higher this week following news of a major partnership. On Tuesday, the small biotech announced a collaboration with United Therapeutics (NASDAQ:UTHR) to develop and market a dry powder formulation of trepostinil for the treatment of pulmonary arterial hypertension. 

United Therapeutics already sells three trepostinil products: Orenitram extended-release tablets, Remodulin injection, and Tyvasi inhaled solution. MannKind is developing an inhaled form of the drug using a similar technology used with its inhaled insulin product, Afrezza. 

The deal was huge for MannKind because it received an upfront payment of $45 million at a point when cash was much needed. In addition, the biotech stands to receive potential milestone payments of up to $50 million plus low double-digit royalties on future sales of the partnered product. 

3. Arrowhead Pharmaceuticals: Hep, hep, hooray

Arrowhead Pharmaceuticals' share price jumped 34% this week on an encouraging update for its hepatitis B drug ARO-HBV. The company announced on Thursday that it would present positive data from a phase 1 study of ARO-HBV at the World Gastroenterologists Summit. 

The data presented included only eight patients receiving the two lowest doses of ARO-HBV. However, the RNA interference therapy appeared to dramatically reduce the levels of hepatitis B virus (HBV) antigens in all of these patients. There are 40 total patients across all cohorts in the study. Arrowhead stated that ARO-HBV was generally well-tolerated by patients.

ARO-HBV holds the potential to cure HBV in many patients. More data will be needed from the other cohorts in the study, though, before ARO-HBV can advance to the next stage of testing.

Are they buys?

ProQR's news was probably the best of all among these three biotechs. The company's plan to begin a pivotal study of QR-110 could mean that a potential approval isn't too far away. It's still early, though. ProQR also isn't the only biotech targeting LCA10. Editas Medicine hopes to begin a phase 1 study soon of its gene-editing therapy EDIT-101. 

I like MannKind's deal with United Therapeutics. It was a smart move that came at a great time. My concern with MannKind, however, is that the company could still have to raise more cash in 2019, which could either increase its debt or lead to more stock dilution.

Arrowhead ranked as one of the best-performing biotech stocks of the first half of 2018. The company's ARO-HBV update added fuel to the fire. As is the case with ProQR, though, Arrowhead still has a long way to go with its pipeline candidates.

My view is that none of these three biotech stocks are great picks for most investors at this point. I'm intrigued by the promise of ProQR's and Arrowhead's drugs. I continue to be impressed by how MannKind CEO Michael Castagna is leading his company. For now, though, I prefer to watch these biotechs from the sidelines. 

Keith Speights owns shares of Editas Medicine. The Motley Fool recommends Editas Medicine. The Motley Fool has a disclosure policy.