Kiniksa Pharmaceuticals International Q2 2026 Earnings Report

Kiniksa Pharmaceuticals International EPS Results

• Actual EPS: $0.30
• Consensus EPS: $0.30
• Beat/Miss: Beat by +$0.00
• One Year Ago EPS: N/A

Kiniksa Pharmaceuticals International Revenue Results

• Actual Revenue: $243.60 million
• Expected Revenue: $226.49 million
• Beat/Miss: Beat by +$17.11 million
• YoY Revenue Growth: N/A

Kiniksa Pharmaceuticals International Announcement Details

• Quarter: Q2 2026
• Date: 7/28/2026
• Time: Before Market Opens
• Conference Call Date: Tuesday, July 28, 2026
• Conference Call Time: 8:30AM ET

Kiniksa Pharmaceuticals International (NASDAQ:KNSA), Inc. is a biopharmaceutical company focused on discovering, acquiring and developing therapeutics for patients suffering from lifethreatening and debilitating immune-mediated diseases. Founded in 2013 and headquartered in Lexington, Massachusetts, Kiniksa applies a patient-centric approach to build a diversified portfolio of marketed medicines and clinical-stage candidates targeting inflammation and immunology. The company’s core mission is to address complex conditions with significant unmet medical needs by advancing both novel and differentiated therapies.

The company’s lead marketed product is Ilaris (canakinumab), an interleukin-1β blocker licensed for the treatment of cryopyrin-associated periodic syndromes, systemic juvenile idiopathic arthritis, adult-onset Still’s disease and Schnitzler syndrome. Beyond Ilaris, Kiniksa’s clinical pipeline includes mavrilimumab, a monoclonal antibody targeting the GM-CSF receptor being investigated for giant cell arteritis; remibrutinib, a selective BTK inhibitor in Phase III studies for chronic spontaneous urticaria; and pozelimab, an anti-C5 monoclonal antibody under development for rare complement-mediated disorders such as paroxysmal nocturnal hemoglobinuria and myasthenia gravis.

Kiniksa operates globally, with commercial and development activities spanning North America, Europe and Asia under various licensing and distribution arrangements. The company is led by Founder and Chief Executive Officer John H. Johnson, who oversees a management team composed of experienced biopharmaceutical executives and scientific leaders. By combining strategic partnerships, disciplined capital allocation and a targeted R&D strategy, Kiniksa aims to deliver therapies that can transform the treatment landscape for patients with serious immune diseases.

Kiniksa Pharmaceuticals International Q2 2026 Earnings Call Transcript

Key Takeaways

• Positive Sentiment: ARCALYST revenue rose 55% year over year to $243.6 million in Q2 2026, an increase of more than $29 million sequentially. Management raised full-year revenue guidance to $980 million–$995 million from $930 million–$945 million.
• Positive Sentiment: Commercial momentum strengthened, with approximately 450 new prescribers and 150 additional repeat prescribers added during the quarter. ARCALYST penetration in the multiple-recurrence population reached approximately 21%, leaving substantial room for expansion.
• Positive Sentiment: Kiniksa advanced KPL-387 into the pivotal PASTEURAL Phase III trial in recurrent pericarditis, evaluating a 300 mg monthly dose after Phase II data showed rapid and sustained treatment response. The company anticipates a potential launch in 2028–2029.
• Neutral Sentiment: KPL-387’s Phase II data showed median treatment response in four days and CRP normalization in eight days, with tolerability consistent with IL-1 pathway inhibition; however, the disclosed analysis was interim and detailed follow-up information remained limited.
• Positive Sentiment: Operating income was $27.2 million, net income was $25.4 million, and quarter-end cash was $525.9 million after approximately $58 million of net cash generation. Collaboration profit increased 68% year over year to $176.1 million despite continued investments in commercialization and clinical development.

Presentation

[Operator]

Thank you for standing by, and welcome to the Kiniksa Pharmaceuticals Q2 2026 earnings conference call. At this time, all participants are in listen only mode. After the speaker's presentation, there will be a question and answer session. To ask a question during the session, you will need to press star one one on your telephone. If your question has been answered and you would like to remove yourself from the queue, simply press star one one again. As a reminder, today's program is being recorded. Now I would like to introduce your host for today's program, Jonathan Kirshenbaum, Senior Manager of Investor Relations. Please go ahead, sir.

[Jonathan Kirshenbaum, Senior Manager of Investor Relations at Kiniksa Pharmaceuticals]

Thank you, operator. Good morning, everyone, and welcome to the Kiniksa Pharmaceuticals Q2 2026 earnings call. A press release highlighting our financial results and recent portfolio execution can be found on our website under the investors section. As for the agenda, our Chief Executive Officer, Sanj K. Patel, will start with an introduction that will be followed by Ross Moat, our Chief Operating Officer, who will provide an update on ARCALYST commercial execution. From there, Kiniksa's Chief Medical Officer, Dr. John Paolini, will review our KPL-387 development program and the ongoing phase II/III clinical trial in recurrent pericarditis. After that, Mark Ragosa, our Chief Financial Officer, will review our Q2 2026 financial results. Finally, Sanj will share closing remarks and kick off the Q&A session.

[Jonathan Kirshenbaum, Senior Manager of Investor Relations at Kiniksa Pharmaceuticals]

Before getting started, please note that we will be making forward-looking statements today that are subject to risks and uncertainties that may cause actual results to differ materially from such statements. A review of these statements and risk factors can be found on this slide, as well as under the caption Risk Factors contained in our SEC filings. These statements speak only as of the date of this presentation and we undertake no obligation to update such statements except as required by law. With that, I will turn it over to Sanj.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Thanks, Jonathan. Good morning or good afternoon, everyone. Kiniksa is in a strong position more than halfway through 2026 as we continue to execute across our portfolio. We continue to make excellent progress with ARCALYST and have advanced the KPL-387 program into the pivotal stage with the initiation of the phase III trial, which we have named PASTEURAL. Additionally, KPL-1161, which is our Fc-modified IL-1 alpha and beta inhibitor with a target profile of quarterly dosing, is progressing well, and the program remains on track to initiate a phase I study by the end of this year. Importantly, we have continued to maintain a robust financial position, which together with strong commercial momentum and key advancements in our development pipeline, positions the company with multiple value-creating drivers in both the near and long term.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Our ongoing execution of the ARCALYST commercial strategy resulted in a meaningful increase in the number of patients on therapy. Robust revenue growth of more than $29 million over the previous quarter drove sales of $243.6 million in the Q2. We continue to build on our strong commercial momentum, and we've raised our full year 2026 revenue guidance from $930 million-$945 million to between $980 million and $995 million. On the clinical side, just this morning, we announced data from the dose focusing portion of the KPL-387 phase II/phase III study in recurrent pericarditis. On the basis of the phase II data, I'm happy to report that we are moving forward with the target profile of a monthly dose into the pivotal phase III portion of the trial.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Today, we also announced that this phase III study has already started and is now enrolling and dosing patients. The ongoing phase III study, PASTEURAL, marks a key milestone in bringing additional treatment options to patients suffering from recurrent pericarditis. This trial follows RHAPSODY, the successful phase III program with ARCALYST, with both trials having the same registrational endpoint of reduction in the risk of pericarditis recurrence. John will share additional details about the phase II data in a moment, as well as provide an overview of the design of this phase III study. We anticipate a potential commercial launch of KPL-387 in the 2028 and 2029 timeframe, extending our leadership in the recurrent pericarditis market so we can help many more patients. With that, I'll turn it over to Ross to review our commercial execution. Ross?

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Thank you, Sanj. In Q2, the Kiniksa commercial team continued to drive strong growth with ARCALYST. Our net revenue was $243.6 million, which is more than $85 million growth versus Q2 of 2025, and more than $29 million growth compared to Q1 2026.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

This represents the largest quarterly net revenue increase since our launch more than five years ago, and is a direct result of the execution of the strategy that we laid out at the beginning of this year. Our commercial approach has helped to change the treatment paradigm for recurrent pericarditis, and we are focused on continuing to unlock future growth for ARCALYST. Over time, we have made disciplined, value-driven investments across our sales infrastructure, as well as innovative strategies that have enabled us to reach more patients. Firstly, we've been diligently ensuring that prescribers have a positive prescribing experience, which encourages deeper prescribing as well as peer-to-peer education to other healthcare professionals. Additionally, we've been invested in machine learning and the use of AI to provide our sales team with insights on not just who to target, but importantly, when to visit and what messages should be delivered.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Secondly, in April of this year, we launched our targeted DTC campaign called Heart's Home. This campaign is aimed at educating and empowering patients who are suffering from recurrent pericarditis to visit their healthcare professional and ask for ARCALYST. So far, the campaign has reached thousands of patients who are suffering from recurrent pericarditis. While it's still in the early stages, we are starting to see encouraging signs of engagement with our campaign and patients visiting their healthcare professional to discuss ARCALYST. Thirdly, our teams have been highly focused on disseminating the 2025 ACC Concise Clinical Guidance for Recurrent Pericarditis. The understanding of this guidance and the recommendation of moving ARCALYST earlier in line after NSAIDs and colchicine and ahead of corticosteroids, has helped to expand the utilization of ARCALYST.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Since our focus on disseminating this publication, we've seen an increase in doctors who have changed their treatment approach and are now using ARCALYST earlier in the disease course. Finally, the commercialization is underpinned by ARCALYST's highly efficacious and well-tolerated profile, along with robust compliance, growing persistence, and an excellent payer approval rate. As of the end of Q2, our penetration into the multiple recurrence population had grown to approximately 21%, compared to around 18% at the end of 2025. This demonstrates both strong growth as well as the substantial opportunity ahead. As mentioned on the last slide, we're seeing continued momentum in the breadth and depth of ARCALYST prescribing, which in Q2 led to significantly higher number of new patient enrollments compared to any quarter since our launch.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Approximately 450 additional healthcare professionals wrote their first ARCALYST prescription in the Q2, bringing the total prescriber base to more than 5,000 launch to date. As a reminder, there are more than 25,000 healthcare professionals across the country who manage recurrent pericarditis patients. Therefore, the opportunity for continued growth is evident. Additionally, the number of healthcare professionals who have written multiple prescriptions increased by approximately 150 compared to Q1 of 2026, meaning that around 29% of the prescriber base have written ARCALYST for two or more patients. The dual acceleration in both new and repeat prescribing led to an increase in patient enrollments, which resulted in a substantial increase to the number of patients on therapy, and illustrates the demand for a highly efficacious treatment that protects patients from suffering unnecessary additional flares.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

As you can hear, we're pleased with the Q2 performance, but we continue to be even more excited by the opportunity that's ahead. With that, I'll turn the call over to Dr. John Paolini to share more information on our KPL-387 program in recurrent pericarditis. John.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

Thank you, Ross. As Sanj mentioned, the pivotal phase III trial of KPL-387 in recurrent pericarditis has now been initiated and is already enrolling and dosing patients. Before that, I'll provide a brief overview of the phase II dose-focusing portion of the trial, data from which affirmed the dose level for phase III. As a reminder, for the phase II/III study, we have combined both portions into a single integrated protocol in order to maximize operational efficiency, thus allowing the phase III portion to begin even while the phase II trial is still ongoing. Phase II is designed to define the PK/PD relationship and provide information on the cadence and magnitude of initial response as well as the durability of effect of defined subcutaneously administered KPL-387 dose levels.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

Up to approximately 80 participants presenting at screening with a pericarditis recurrence despite treatment with NSAIDs and colchicine are randomized equally into four arms to receive subcutaneously administered KPL-387 at 100 milligrams or 300 milligrams dosed biweekly or once monthly. Concomitant treatment with conventional oral therapies is weaned and discontinued within two weeks to attain KPL-387 monotherapy. The primary endpoint of the phase II dose-focusing study is time to treatment response through 24 weeks, defined as an NRS score of less than or equal to two on the 11-point daily pericarditis NRS pain scale and normalization of C-reactive protein, a marker of pericardial inflammation. The data we announced today show that the KPL-387 300-mg monthly dose level demonstrated rapid and sustained onset of action with durable efficacy throughout the monthly dosing interval, affirming the 300-mg monthly dose being evaluated in the phase III study, PASTEURAL.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

Specifically, in this analysis, median time to treatment response was four days with a 95% confidence interval of three - six days. Median time to pain response was four days with a confidence interval of three - six days, and median time to CRP normalization was eight days with a confidence interval of seven - nine days. The cadence and magnitude of these reductions in pain and inflammation are consistent with prior studies which supported ARCALYST approval in recurrent pericarditis. KPL-387 was generally well-tolerated, consistent with the well-known safety profile of IL-1 pathway inhibition. Regarding the other dose levels in the study not selected for phase III, the 100-mg subcutaneous biweekly and monthly dose levels showed some effect, but not at the level to support further study. The KPL-387 300-mg biweekly dose level was efficacious without incremental benefit above the monthly dose level.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

The totality of data available supported the initiation of PASTEURAL with the 300-mg subcutaneous monthly dose level. The PASTEURAL design should look familiar based upon our prior work in RHAPSODY. This pivotal phase III trial is a placebo-controlled, event-driven, randomized withdrawal study designed to measure the reduction in risk of pericarditis recurrence as the primary demonstration of KPL-387 efficacy for the label. The primary efficacy endpoint is time to first adjudicated pericarditis recurrence during the randomized withdrawal period. The trial will enroll up to approximately 85 participants experiencing a pericarditis recurrence despite conventional oral therapies into a single blind run-in period, during which KPL-387 is initiated, and oral therapies are weaned and discontinued. Participants are blinded to the duration of the run-in period.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

Subsequently, participants who respond to KPL-387 in the run-in period then enter the randomized withdrawal period in which they either continue receiving KPL-387 300 milligrams once monthly or switch to placebo. Upon closure of the randomized withdrawal period, participants may be eligible to continue into a long-term extension. As we have mentioned, our goal is to bring this potential new additional treatment option to patients in the 2028 - 2029 timeframe. I will now turn the call over to Mark to cover our Q2 financials. Mark?

[Mark Ragosa, CFO at Kiniksa Pharmaceuticals]

Thanks, John. This morning, I'll walk us through our Q2 2026 financial performance and highlight the key drivers behind the results. As always, detailed financial information is available in today's press release. The quarter reflected strong execution with continued momentum across our commercial business, advancement of our development pipeline, and further strengthening of our financial position. Starting on the left-hand side of this slide with the income statement, ARCALYST revenue grew 55% year-over-year to $243.6 million in the Q2. As you heard from Ross, this growth was driven by continued expansion in new and repeat prescribers as well as patient enrollments. Operating expense growth year-over-year was driven by several factors.

[Mark Ragosa, CFO at Kiniksa Pharmaceuticals]

Higher cost of goods sold due to ARCALYST revenue growth, increased collaboration expenses aligned with higher ARCALYST revenue and collaboration profit, higher R&D, primarily due to the increased KPL-387 clinical trial costs as well as manufacturing costs, also increased preclinical development investment. Lastly, additional SG&A, primarily driven by investment associated with the commercialization of ARCALYST. Together, these factors contributed to year-over-year increases in operating income and net income, which were $27.2 million and $25.4 million, respectively. The calculation for ARCALYST collaboration profit drives total collaboration expenses is on the right-hand side of the slide. Here, we continue to leverage disciplined commercial investment as ARCALYST collaboration profit grew faster than sales on a year-over-year basis, increasing 68% to $176.1 million.

[Mark Ragosa, CFO at Kiniksa Pharmaceuticals]

Turning next to cash, at the bottom of the slide, we ended the Q2 with a $525.9 million cash balance, representing approximately $58 million of net cash generation for the period. Looking ahead, we believe our operating plan enables us to continue helping patients while creating additional value over both the near and longer term. With that, I'll turn the call back to Sanj for closing remarks.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Thanks, Mark. As you've heard, Kiniksa is well-positioned to build significant future value as we grow our IL-1 alpha and beta inhibition franchise. We are dedicated to helping as many patients as possible with ARCALYST and to advancing the development of our clinical portfolio in order to bring additional therapies to patients. With that, I'll now turn the call back to the operator for questions.

[Operator]

Certainly. Once again, if you have a question at this time, please press star one one on your telephone. Our first question comes from the line of Nicholas Lorusso from TD Cowen. Your question please.

[Nicholas Lorusso, VP at TD Cowen]

Thanks very much for taking our question, congrats on the very strong quarter, guys. As you guys mentioned, this was the strongest quarter of ARCALYST absolute sales growth since launch. Just wanted to dive into what drove this growth specifically in Q2, could this level of growth continue throughout the rest of the year and into next year? Thanks.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Thanks, Nick. I'll say a few comments, I'm sure I'll leave it to Ross to dive into some detail. Look, as always, it's continuing to execute across the entire commercial strategy and overall growing the adoption of IL-1 pathway inhibition as the preferred treatment for recurrent pericarditis. That continues to happen every quarter. Certainly, this quarter, Ross will dive into the number of new unique prescribers we've had this quarter, as well as the number of new repeat prescribers and the new enrollments. Ultimately, it's a matter of just continuing to penetrate into the total population, which we're doing. Obviously, the total duration of therapy is very important. That's about in line really with the median duration of the disease, about three years. Ultimately penetrating into that. As we just reported, we're now around 21% penetrated into the multiple recurrence population.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

That to me represents a meaningful opportunity ahead, that's what we're focused on. Very excited about it. Ross, why don't you dive into some of the drivers and the actual numbers across those metrics, the special sauce is just continuing to execute.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Thanks, Sanj, thanks for the question, Nick. I think that's absolutely right. This is a culmination of a lot of work across all our commercial and cross-functional teams at this point, and where we've got to really understanding the recurrent pericarditis market and really just generally executing flawlessly across the board. Really kudos to all of the team that have been able to help so many patients throughout Q2. Ultimately, we've seen a substantial uplift in the number of both new prescribers and new repeat prescribers. As Sanj said, we have more than 450 new prescribers come into the total prescribing base in Q2, more than 150 new repeat prescribers, meaning they've prescribed for two or more patients in the quarter.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Ultimately, that's grown the number of patients that are on therapy, which led to both the results in Q2 being the highest number of nice new revenue, incremental revenue that we've had in any quarter since launch, as well as the highest number of new prescribers. Ultimately, some of the driving factors underneath that, as well as some of the actions that we've put into place around investing in AI and machine learning, trying to make our field team even more effective than they historically have been. Knowing just not only who to call upon in a very traditional targeting approach, but more importantly now seeing when to call upon doctors and some of that is through claims analysis alerts, but importantly predictive alerts as well of when patients may be coming into flare and visiting particular healthcare professionals.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

As you know, we've also invested in the DTC campaign, that's starting to show some early signs of success, driving patients into the clinic to ask specifically for ARCALYST. I think the third point that's worth mentioning is around the dissemination of the ACC Concise Clinical Guidance, which actually was published in August of last year. Generally speaking, because these recurrent pericarditis patients are very widely dispersed around the country, many of the general cardiologists are not familiar with the ACC Concise Clinical Guidance for recurrent Pericarditis. Our dissemination efforts in really explaining what that guidance document means, and how IL-1 inhibition is now placed after NSAIDs and colchicine use and prior to corticosteroids, has been a key part in the transformation of really changing the treatment paradigm and being able to help many more patients.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

I think all said, it's really rolled up to just ongoing solid execution across the team and acknowledging that even now, five years plus into the launch, there remains very significant opportunity for ARCALYST moving forward.

[Nicholas Lorusso, VP at TD Cowen]

Thank you very much. It's all very helpful.

[Operator]

Thank you. Our next question comes from the line of Eva Fortea from Wells Fargo. Your question, please.

[Eva Fortea, Executive Director at Wells Fargo]

Hey, good morning. Thanks for taking our question and congrats on the quarter. Two quick ones from us. On your prepared remarks, you mentioned a higher number of new patient enrollment for ARCALYST this quarter. Is there a specific patient profile that you're seeing coming at this stage of the launch? The follow-up was, can you comment on the gross to net for the quarter? Thanks.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Ross, why don't you start with the beginning part on Mark, if you can comment on the Go-To-Market?

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Yeah, absolutely. Let's do that. Thank you, Eva, for the question. We haven't really seen any changes in the actual patient profiles as such, whether that's through kind of demographics of the patients to what level we know about that or the type of institutions or healthcare professionals that are prescribing. It's still really across the board, kind of academic centers, more rural centers. The opportunity, I think, is still very broad across the country. We haven't really seen a change in patient profile or phenotype to what we've seen. I think this is really more through just a greater understanding of recurrent pericarditis, greater efforts from the cardiology community to really differentiate between the first index pericarditis episode and actually when this becomes recurrent pericarditis.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

You know, historically, the misdiagnosis and underdiagnosis rate is pretty substantial, and patients go through seeing many healthcare professionals before getting the recurrent pericarditis diagnosis. We've seen that, I think, improve over time. I think that's really everything. That there's no major changes and just happy to see more patients getting the help that they really need and deserve.

[Mark Ragosa, CFO at Kiniksa Pharmaceuticals]

I guess, David, your second question regarding gross to net in the quarter. Historically, gross to net does move lower sequentially in the Q2. That was the case again this year. Year to date, gross to net is 7.2%, down from 8.6% in the Q1, with the main driver being lower co-pay due to the changes that we made to our support program at the beginning of the year. I think as you look throughout the rest of the year here, we don't provide specific gross to net guidance, but we do anticipate co-pay support to continue to be favorable to gross to net on an annual basis, with the majority of the impact having taken place in the Q1. Additionally, we do expect sort of the normal pattern to hold here.

[Mark Ragosa, CFO at Kiniksa Pharmaceuticals]

Absent any prior period reserve adjustments, our gross to net historically has been highest in the Q1, lower in Q2 and Q3, then works a little bit higher in the Q4 as industry dynamics begin to play a factor. I'll leave it there.

[Eva Fortea, Executive Director at Wells Fargo]

Very helpful. Thanks.

[Operator]

Thank you. Our next question comes from the line of Geoff Meacham from Citi. Your question, please.

[Geoff Meacham, Managing Director at Citi]

Great. Hey, guys. Thanks for the question. Congrats on the data and the quarter. Just have a couple. The first on 387, now that you have the phase II data in hand and with commercial knowledge of the market, is there anything you guys have embedded in the phase III, perhaps to further differentiate the profile of 387? Then second question I know I usually ask, but wanted to check on demand trends from the first recurrence population for ARCALYST. Is there maybe some element of that driving this quarter? Thank you.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

John Paolini, I'm not sure if you want to comment on the phase III study. Essentially, obviously, we're pretty excited about the phase II results we've seen. We're obviously now moving into phase III. As we've said, we're excited about the target profile of KPL-387, potential for monthly dosing, liquid formulation. That in and of itself, I think is very exciting. Obviously, the data will be the data from the phase III. We're just focusing on really getting through the rest of the enrollment on the phase III study and hopefully seeing the results and being on the market in the 2028, 2029 time frame. John Paolini, any comments from the phase III study?

[John Paolini, CMO at Kiniksa Pharmaceuticals]

No. I would say that the profile, as Andrew mentioned, of KPL-387 that we're taking into the phase III study is one that we're very excited about. Rapid onset of action, durable efficacy throughout the monthly dosing interval that's being studied in phase III in PASTEURAL. That sets us up in an excellent position for the pivotal phase III trial. The design of the phase III trial is one that we understand well and that is well understood in the scientific community as a randomized withdrawal study design. We are prepared to execute on that and to bring the trial forward.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Thanks, Geoff. Appreciate your question. If I just answer your question on ARCALYST, thinking about the demand in the first recurrence population, we've seen that physicians are continuing to utilize ARCALYST broadly across the very broad label that we have. Which is, as you know, is agnostic to the number of recurrences that a patient has suffered from. There's around 40,000 patients in any given year that fit within the recurrent pericarditis label. When you break that down, we have about 80% of all new patient prescribing happening in the two plus recurrence. That's about 80% of new prescriptions that are coming in in a quarter are for patients that are on their second or more recurrence. That's a 14,000 patient population. Based upon that population, that's where we mentioned that we're now penetrated around 21% into that opportunity.

[Ross Moat, COO at Kiniksa Pharmaceuticals]

That's not accounting for the patients to your question directly, that are on their first recurrence. Again, fitting within the label, that's a larger patient group. It's around 26,000 of the 40,000 patients. We see about 20% of the ARCALYST prescriptions in Q2 that are within that patient group. That's been growing over time, and I think some of that reflects the acknowledgement of the broad label, the increasing confidence of using ARCALYST, and ultimately the ongoing opportunity that there is ahead. Thank you. Thank you.

[Operator]

Thank you. Our next question comes from the line of Anupam Sharma from JPMorgan. Your question please.

[Anupam Sharma, Analyst at JPMorgan]

Hey, guys. Thanks so much for taking the question, and congrats on all the progress. Just wanted to follow up on Geoff Meacham's question here. On KPL-387 300 mg dose, when I look at time to response, pain, CRP, I compare it to the RHAPSODY New England Journal of Medicine paper, the run-in period for ARCALYST, it looks very in line-ish, ± a day or so. Is that a fair assessment? Can you remind us what your market research suggests a monthly regimen could mean commercially? Thanks so much.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

John, why don't you start, Ross, you can jump in.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

Sounds great. Thank you, Anupam, for the question. Yes, we would concur that the data that we have shown from the phase II trial in terms of time to treatment response, time to pain response, and time to CRP normalization are very robust and are consistent with what has been seen previously in trials that supported rilonacept approval in recurrent pericarditis, especially when one takes a confidence interval approach to looking at the numbers with your point estimates.Ross?

[Ross Moat, COO at Kiniksa Pharmaceuticals]

Yeah. Thank you, Anupam. Yes, we did previously share some market research around thoughts from both patients and healthcare professionals on the target product profile of KPL-387 versus current commercial and other investigational therapies. Really that showed that both to a high degree for both the patients and the healthcare professionals, they were pretty excited about the KPL-387 target product profile, with around 75% of patients saying that they would prefer the KPL-387 target product profile over current commercial or available or investigational therapies. Additionally, around 92% of healthcare professionals indicated a high likelihood to prescribe for new patients in the context of the target product profile. Additionally, the potential availability of another IL-1 therapy could also expand the pool of patients for IL-1 inhibition overall with the monthly target product profile.

[Operator]

Thank you. Our next question comes from the line of Paul Choi from Goldman Sachs. Your question please.

[Paul Choi, Analyst at Goldman Sachs]

Hi. Thank you. Good morning, thanks for taking our questions, and congrats on the quarter and progress. My first question is on the commercial side, I was just curious if you're thinking about adding incremental headcount to your sales force at this point, just given the commercial momentum, or is the plan to continue to leverage AI and the advancement of the ACC clinical guidelines? My second question is on KPL-387, specifically the transition study for patients who are stable. Can you maybe highlight what you're trying to show there and what data are needed to support a potential switch strategy from ARCALYST down the road? Thank you.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Maybe I'll start, John, if you can take the rest. Thanks, Paul. Look, we're always looking at our sales force analytics and working out the best way to reach these physicians and healthcare professionals.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

That's an ongoing basis for us. I don't think there's anything to report really on that side. As Ross mentioned, we continue to leverage the AI and machine learning and digital marketing, which has been really helpful. Again, it's just really one part. There are a multitude of ways that we've got to continue to keep working to continue to penetrate into the total population, which we're doing. It's really a matter of no one size fits all. You've got to continue to execute across all those functions. We'll continue to crack on. Clearly, the 21% penetration so far tells you there's an awful lot more work to do, and that's what we're geared up to do. We'll do it with the best way we can across all those different areas and hopefully continue to report information to you going forward.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

Thank you, Paul, for your question. Yes, the KPL-387 transition to monotherapy dosing and administration study. It was a phase II study designed to provide supplemental information for the label and to provide basically the information to assist clinicians as they move across different therapies, if you will, for recurrent pericarditis. That trial is designed to, with different dosing regimens, to test that efficacy and safety as patients move from regimens of NSAIDs and colchicine or corticosteroids or IL-1 pathway inhibitors, including anakinra and rilonacept. At the end of that study, with these different dosing paradigms having been tested, that enables the writing, if you will, of the dosing and administration section of the label in order to allow patients to move smoothly across therapeutic lines.

[Paul Choi, Analyst at Goldman Sachs]

Okay, great. Thank you.

[Operator]

Thank you. Our next question comes from the line of David Nierengarten from Wedbush. Your question please.

[David Nierengarten, Analyst at Wedbush]

Hey, thanks for taking the question. I have one on 387. I have maybe two. First, just what was the kind of median follow-up? Was it the full six months for these patients or something else? If you saw any recurrences in the population in the study in the 300 milligram arms or any of the other ones actually. Thanks.

[John Paolini, CMO at Kiniksa Pharmaceuticals]

Yeah. No, thank you, David, for the question. The data that were obtained for this analysis, it was an interval analysis of the ongoing study, and as such, the disclosure is limited. What we can say is that we have harvested this information to affirm the 300 mg monthly dose, certainly beyond the monthly dosing interval, right, in order to show that at the trough, if you will, of the monthly dosing interval, the treatment effect is robust. Other than that is the limit of what we have said. What we have also said, though, is that the 300 mg biweekly dose level, which of course delivers more drug, did not provide incremental benefit above the 300 mg monthly dose.

[David Nierengarten, Analyst at Wedbush]

Okay. Thanks.

[Operator]

Thank you. This does conclude the question and answer session of today's program. I'd like to hand the program back to Sanj for any further remarks.

[Sanj Patel, CEO and Chairman of the Board at Kiniksa Pharmaceuticals]

Thank you, operator. Well, we better crack on. Thank you for all the questions today, joining the call. We look forward to the remainder of the year and to providing additional updates in the future. Thank you.

[Operator]

Thank you, ladies and gentlemen, for your participation in today's conference. This does conclude the program. You may now disconnect. Good day

Participants

Executives

• Sanj Patel, CEO and Chairman of the Board
• Ross Moat, COO
• John Paolini, CMO
• Mark Ragosa, CFO

Analysts

• Jonathan Kirshenbaum, Senior Manager of Investor Relations at Kiniksa Pharmaceuticals
• Nicholas Lorusso, VP at TD Cowen
• Eva Fortea, Executive Director at Wells Fargo
• Geoff Meacham, Managing Director at Citi
• Anupam Sharma, Analyst at JPMorgan
• Paul Choi, Analyst at Goldman Sachs
• David Nierengarten, Analyst at Wedbush