Are penny stocks a must-have or a must-avoid? Well, that depends on who you ask. There’s no middle ground when it comes to these tickers trading for less than $5 per share; those on the Street are either fans or harsh critics.Both sides make sense. The naysayers argue that the bargain price is just too good to be true, with it potentially indicating there are problems hiding beneath the surface like weak fundamentals or overwhelming headwinds.However, the investors that are pro-penny stocks just can’t get enough of them. Not only do the low prices mean that you get more bang for your buck, but also even minor share price appreciation can translate to huge percentage gains, and thus, major returns.While incredibly enticing, the risk is clear. So, you have to do your homework. Using TipRanks’ database, we pinpointed three compelling penny stocks, as determined by Wall Street pros. Each has earned a “Strong Buy” consensus rating from the analyst community and brings massive growth prospects to the table. We’re talking about triple-digit upside potential here. Infinity Pharmaceuticals (INFI)Kicking off our list, we have Infinity Pharmaceuticals, which develops biologically active and selective drug candidates directed against biologically well-validated targets. Based on multiple potentially significant clinical catalysts as well as its $0.99 share price, several members of the Street think that now is the right time to pull the trigger. Representing Oppenheimer, 5-star analyst Kevin DeGeeter came away from management’s Q2 2020 update even more excited about the company’s prospects. During the update, INFI announced that the protocol modification for the MARIO-275 study, which involved lowering the dose of IPI-549 from 40mg to 30mg, payed off, with it resulting in an improved AE profile. Additionally, undisclosed positive responses from the open label MARIO-3 TNBC cohort could be released at a medical meeting in Q4 2020.“As such, we now see potential for material clinical catalysts for both MARIO-275 and MARIO-3 in Q4 2020. While our investment thesis remains focused on use of IPI-549 in combo with Nivo for urothelial cancer, we acknowledge the TNB cohort from MARIO-3 may offer a faster path to clinical proof-of-concept,” DeGeeter commented.Looking more closely at the data for MARIO-275, for the first 42 patients, IDMC identified elevated liver enzyme in seven patients, or 14% (five with Grade 3 and two with Grade 4). On top of this, six patients didn’t experience sequela and since the dose was reduced, no clinically significant liver toxicity has been witnessed. According to DeGeeter, INFI is slated to reassess the continuation of MARIO-275 around the end of 2020, “which will allow investigators to complete up to 3 additional scans at lower dose of 30mg before evaluating risk/benefit of the combination in urothelial cancer.”As for MARIO-3, the company believes that even though COVID-19 has impacted enrollment, positive early results might help speed up the process. To this end, DeGeeter rates INFI an Outperform (i.e. Buy) along with a $3 price target. This implies shares could soar 203% in the next year. (To watch DeGeeter’s track record, click here)What do other analysts have to say? As the stock has received 3 Buy ratings and 1 Hold in the last three months, the word on the Street is that INFI is a Strong Buy. At $2.17, the average price target brings the upside potential to 119%. (See INFI stock analysis on TipRanks)OncoSec Medical (ONCS)Using its plasmid DNA delivery platform, OncoSec Medical develops immunotherapy cancer candidates that could potentially provide safer and more effective cancer treatments. Given its promising technology, the $4.01 share price looks like a steal to some Wall Street pros.Dawson James analyst Jason Kolbert cites TAVO, the company's plasmid-based interleukin-12 that’s administered locally through its electroporation gene delivery system, as a key component of his bullish thesis. TAVO is able to cause the local expression of IL-12, essentially turning “cold” tumors “hot” in skin cancer. This makes checkpoint therapies such as Keytruda (pembrolizumab) effective.Digging a bit deeper into the data, during a Phase 2 trial in immunologically quiescent melanoma patients treated with intratumoral TAVO plus pembrolizumab, 41% of patients “were observed to have best overall objective response rate - ORR (CR+PR), with 36% displaying complete responses to treatment of their target lesions.” Additionally, Kolbert points out that the combination was well tolerated and the adverse events resembled those of pembrolizumab alone.When it comes to the Phase 2 trial in metastatic melanoma, Kolbert noted, “Here too, intratumoral TAVO was well tolerated and led to systemic immune responses in advanced melanoma patients. While tumor regression and increased immune infiltration were observed in treated as well as untreated/distal lesions, adaptive immune resistance limited the response.”The implication of these results? “We ultimately expect to see expansion into the broader Melanoma market, as well as other indications such as Squamous Cell Carcinoma Head and Neck Cancer (SCCHNCC) and Triple Negative Breast Cancer (TNBC),” Kolbert explained.It should come as no surprise, then, that Kolbert stands squarely with the bulls. To this end, he rates ONCS a Buy and gives it a $10 price target. Should his thesis play out, a potential twelve-month gain of 150% could be in the cards. (To watch Kolbert’s track record, click here) Other analysts are also optimistic about the cancer drug maker. ONCS' Strong Buy consensus rating breaks down into 3 Buys and no Holds or Sells. In addition, the $8.17 average price target puts the upside potential at 104%. (See OncoSec stock analysis on TipRanks)Trevi Therapeutics (TRVI)Moving on to another healthcare name, Trevi Therapeutics focuses on the development of Nalbuphine ER, with it hoping to improve the lives of patients suffering from serious neurologically-mediated conditions. Currently going for $4.45 apiece, its share price presents investors with a unique buying opportunity, according to the analysts.Among the TRVI bulls is BMO’s Gary Nachman. The analyst tells clients that the company wrapped up its sample size re-estimation (SSRE) analysis for the ongoing Phase 2b/3 PRISM trial for Haduvio (Nalbuphine ER) in lead indication prurigo nodularis (PN).Based on the independent data monitoring committee’s recommendation, TRVI can now increase patient enrollment from 240 to 360 in order to maintain statistical powering for the primary endpoint. Calling this a “key inflection point,” Nachman believes the result “suggests Haduvio has likely demonstrated some efficacy thus far, but the trial's adaptive design now enables TRVI to de-risk it further and have the best chance of achieving success (data now Q4 2021).”What was behind the recommendation? The decision was based on the SSRE analysis of 108 patients that completed a 14-week blinded treatment period and were evaluable for the primary endpoint (an improvement on the Worst Itch Numerical Rating Scale). The larger sample size will allow TRVI to keep the trial’s 90% statistical powering for the primary endpoint. Expounding on this, Nachman stated, “While the increased enrollment to 360 is the maximum allowed under trial’s protocol, it is not so surprising to us given that PN is a challenging condition, primary endpoint is a bit of a higher bar than prior Phase 2, and factoring elevated patient discontinuations in prior Phase 2 primarily related to mild/moderate transient AEs during two-week titration period that TRVI has been trying to manage with physician/patient education.”Adding to the good news, management said that enrollment has been ramping up after most COVID-19 screening and enrollment restrictions were removed, with the process set to be completed in Q3 2021. Nachman argues that its discontinuation of underperforming sites and activation of new sites could also help. He added, “Further, there is much less competition for PN patients following Menlo Therapeutics’ completion of its Phase 3 trials in PN with serlopitant (failed to demonstrate efficacy and leaves Haduvio as only oral in development for PN).”If that wasn’t enough, TRVI is hoping to restart the chronic cough in IPF Phase 2 trial, potentially in the fall. Nachman sees this as an “underappreciated opportunity,” and points out recent data demonstrates “pharmacological evidence of Nalbuphine as a cough suppressant using it to treat sufentanil-induced cough during anesthesia.”In line with his optimistic take, Nachman rates TRVI an Outperform (i.e. Buy). Along with the call, he has a $13 price target on TRVI, implying upside potential of 196%. (To watch Nachman’s track record, click here)Do other analysts agree? They do. Only Buy ratings, 4, in fact, have been issued in the last three months, so the consensus rating is a Strong Buy. Given the $10.75 average price target, shares could soar 142% in the next year. (See Trevi stock analysis on TipRanks)To find good ideas for penny stocks trading at attractive valuations, visit TipRanks’ Best Stocks to Buy, a newly launched tool that unites all of TipRanks’ equity insights.Disclaimer: The opinions expressed in this article are solely those of the featured analysts. The content is intended to be used for informational purposes only. It is very important to do your own analysis before making any investment.